Adrenaline has an important use when injected intramuscularly or intravenously in the treatment of ANAPHYLAXIS. Many patients prone to this condition are prescribed a pre-assembled adrenaline-containing syringe and needle (Min-i-Jet, Epipen) and are taught how to self-administer in an emergency. Adrenaline may be applied directly to wounds, on gauze or lint, to check haemorrhage; injected along with some local anaesthetic it permits painless, bloodless operations to be performed on the eye, nose, etc. Nowadays it is rarely, if ever, used hypodermically and is no longer given to treat ASTHMA. In severe cardiac arrest, adrenaline (1 in 10,000) by central intravenous injection is recommended. It can be given through an endotracheal tube as part of neonatal resuscitation.... adrenaline
A severe or life-threatening reaction is often termed ANAPHYLAXIS. Many immune mechanisms also contribute to allergic disorders; however, adverse reactions to drugs, diagnostic materials and other substances often do not involve recognised immunological mechanisms and the term ‘hypersensitivity’ is preferable. (See also IMMUNITY.)
Adverse reactions may manifest themselves as URTICARIA, wheezing or di?culty in breathing owing to spasm of the BRONCHIOLES, swollen joints, nausea, vomiting and headaches. Severe allergic reactions may cause a person to go into SHOCK. Although symptoms of an allergic reaction can usually be controlled, treatment of the underlying conditon is more problematic: hence, the best current approach is for susceptible individuals to ?nd out what it is they are allergic to and avoid those agents. For some people, such as those sensitive to insect venom, IMMUNOTHERAPY or desensitisation is often e?ective. If avoidance measures are unsuccessful and desensitisation ine?ective, the in?ammatory reactions can be controlled with CORTICOSTEROIDS, while the troublesome symptoms can be treated with ANTIHISTAMINE DRUGS and SYMPATHOMIMETICS. All three types of drugs may be needed to treat severe allergic reactions.
One interesting hypothesis is that reduced exposure to infective agents, such as bacteria, in infancy may provoke the development of allergy in later life.
Predicted developments in tackling allergic disorders, according to Professor Stephen Holgate writing in the British Medical Journal (22 January 2000) include:
Identi?cation of the principal environmental factors underlying the increase in incidence, to enable preventive measures to be planned.
Safe and e?ective immunotherapy to prevent and reverse allergic disease.
Treatments that target the protein reactions activated by antigens.
Identi?cation of how IgE is produced in the body, and thus of possible ways to inhibit this process.
Identi?cation of genes affecting people’s susceptibility to allergic disease.... allergy
Penicillin is a beta-lactam antibiotic, one of a group of drugs that also includes CEPHALOSPORINS. Drugs of this group have a four-part beta-lactam ring in their molecular structure and they act by interfering with the cell-wall growth of mutliplying bacteria.
Among the organisms to which it has been, and often still is, active are: streptococcus, pneumococcus, meningococcus, gonococcus, and the organisms responsible for syphilis and for gas gangrene (for more information on these organisms and the diseases they cause, refer to the separate dictionary entries). Most bacteria of the genus staphylococcus are now resistant because they produce an enzyme called PENICILLINASE that destroys the antibiotic. A particular problem has been the evolution of strains resistant to methicillin – a derivative originally designed to conquer the resistance problem. These bacteria, known as METHICILLINRESISTANT STAPHYLOCOCCUS AUREUS (MRSA), are an increasing problem, especially after major surgery. Some are also resistant to other antibiotics such as vancomycin.
An important side-e?ect of penicillins is hypersensitivity which causes rashes and sometimes ANAPHYLAXIS, which can be fatal.
Forms of penicillin These include the following broad groups: benzylpenicillin and phenoxymethyl-penicillin; penicillinase-resistant penicillins; broad-spectrum penicillins; antipseudomonal penicillins; and mecillinams. BENZYLPENICILLIN is given intramuscularly, and is the form that is used when a rapid action is required. PHENOXYMETHYLPENICILLIN (also called penicillin V) is given by mouth and used in treating such disorders as TONSILLITIS. AMPICILLIN, a broad-spectrum antibiotic, is another of the penicillins derived by semi-synthesis from the penicillin nucleus. It, too, is active when taken by mouth, but its special feature is that it is active against gram-negative (see GRAM’S STAIN) micro-organisms such as E. coli and the salmonellae. It has been superceded by amoxicillin to the extent that prescriptions for ampicillin written by GPs in the UK to be dispensed to children have fallen by 95 per cent in the last ten years. CARBENICILLIN, a semi-synthetic penicillin, this must be given by injection, which may be painful. Its main use is in dealing with infections due to Pseudomonas pyocanea. It is the only penicillin active against this micro-organism which can be better dealt with by certain non-penicillin antibiotics. PIPERACILLIN AND TICARCILLIN are carboxypenicillins used to treat infections caused by Pseudomonas aeruginosa and Proteus spp. FLUCLOXACILLIN, also a semi-synthetic penicillin, is active against penicillin-resistant staphylococci and has the practical advantage of being active when taken by mouth. TEMOCILLIN is another penicillinase-resistant penicillin, e?ective against most gram-negative bacteria. AMOXICILLIN is an oral semi-synthetic penicillin with the same range of action as ampicillin but less likely to cause side-effects. MECILLINAM is of value in the treatment of infections with salmonellae (see FOOD POISONING), including typhoid fever, and with E. coli (see ESCHERICHIA). It is given by injection. There is a derivative, pivmecillinam, which can be taken by mouth. TICARCILLIN is a carboxypenicillin used mainly for serious infections caused by Pseudomonas aeruginosa, though it is also active against some gram-negative bacilli. Ticarcillin is available only in combination with clarulanic acid.... penicillin
Shock may result from loss of blood or plasma volume. This may occur as a result of haemorrhage or severe diarrhoea and vomiting. It may also result from peripheral pooling of blood due to such causes as TOXAEMIA or ANAPHYLAXIS. The toxaemia is commonly the result of a SEPTICAEMIA in which leakage through capillaries reduces circulating blood volume. Another form is called cardogenic shock, and is due to failure of the heart as a pump. It is most commonly seen as a result of myocardial infarction (see under HEART, DISEASES OF).
If failure of adequate blood ?ow to vital organs is prolonged, the effects can be disastrous. The ischaemic intestine permits the transfer of toxic bacterial products and proteins across its wall into the blood; renal ISCHAEMIA prevents the maintenance of a normal electrolyte and acid-base balance.
Treatment If the shock is a result of haemorrhage or diarrhoea or vomiting, replacement of blood, lost ?uid and electrolytes is of prime importance. If it is due to septicaemia, treatment of the infection is of paramount importance, and in addition, intravenous ?uids and vasopressor drugs will be required. Cardiogenic shock is treated by attention to the underlying cause. Full intensive care is likely to be required, and arti?cial ventilation and DIALYSIS may both be needed.... shock
Adverse effects can be divided into types. First, those which are closely related to the concentration of the drug and accord with what is known of its PHARMACOLOGY. These so-called type A (augmented pharmacological) effects are distinguished from type B (bizarre) effects which are unpredictable, usually rare, and often severe. ANAPHYLAXIS is the most obvious of these; other examples include bone-marrow suppression with CO-TRIMOXAZOLE; hepatic failure (see HEPATITIS) with SODIUM VALPROATE; and PULMONARY FIBROSIS with AMIODARONE. A more comprehensive classi?cation includes reactions type C (chronic effects), D (delayed effects – such as teratogenesis or carcinogenesis) and E (end-of-dose effects – withdrawal effects). Examples of adverse reactions include nausea, skin eruptions, jaundice, sleepiness and headaches.
While most reported adverse reactions are minor and require no treatment, patients should remind their doctors of any drug allergy or adverse e?ect they have suffered in the past. Medical warning bracelets are easily obtained. Doctors should report adverse effects to the authorities – in the case of Britain, to the Committee on Safety of Medicines (CSM), using the yellow-card reporting machinery.... adverse reactions to drugs
There is little evidence that any one antihistamine is superior to another, and patients vary considerably in their response to them. The antihistamines di?er in their duration of action and in the incidence of side-effects such as drowsiness. Most are short-acting, but some (such as promethazine) work for up to 12 hours. They all cause sedation but promethazine, trimeprazine and dimenhydrinate tend to be more sedating while chlorpheniramine and cyclizine are less so, as are astemizole, oxatomide and terfenadine. Patients should be warned that their ability to drive or operate machinery may be impaired when taking these drugs, and that the effects of ALCOHOL may be increased.... antihistamine drugs
Habitat: In damp places throughout the plains and low hills in India.
English: Sneezewort.Ayurvedic: Kshavaka, Chhikkini, Chhikkikaa.Folk: Nak-chhikani.Action: Used for the treatment of rhinitis, sinusitis, nasopharyngeal tumors and obstructions, asthma and cold; also used in hemicrania.
The plant extract showed a good an- titussive and expectorant activity on mice. The flavonoids, sesquiterpenes and amide exhibited significant antial- lergy activity in passive cutaneous anaphylaxis (PCA) test.... centipeda orbicularisHabitat: The sub-tropical Himalayas of Kumaon and Nepal; cultivated in Andhra Pradesh.
Ayurvedic: Gandira (Achyranthes aquatica Br. is also equated with Gandira). (Doubtful synonym.)Folk: Garmar (Gujarat), Gurmal.Action: Root and leaf—spasmolytic, antithrombotic, anti-inflammatory, lipolytic.
In experimental amoebiasis of rats, the root powder and ethanolic extract showed amoebicidal activity against Entamoeba histolytica.An alcoholic extract of the roots and essential oil from it, were found to inhibit passive cutaneous anaphylaxis in the mouse and rat.The plant produces the labdane diterpenoid, forskolin in its tuberous roots.Forskolin was discovered during a screening of medicinal plants by Central Drug Research Institute, Luc- know, India, in 1974. (Planta Medica, 1985, 51, 473-477.) The screening revealed the presence of a hypoten- sive and spasmolytic principle, named coleonol (later the name was changed to forskolin). The basic mechanism of forskolin is the activation of an enzyme, adenylate cyclase, which increases the amount of cyclic adeno- sine monophosphate (cAMP) in cells. Raised intracellular cAMP level exhibits following physiological effects : inhibition of platelet activation and degranulation; inhibition of mast cell degranualation and histamine release; relaxation of the arteries and other smooth muscles; increased insulin secretion; increased thyroid function; increased lipolysis.Forskolin, in clinical studies, reduced intraocular pressure when it was applied to the eyes for treating glaucoma. It has been shown to be a direct cerebral vasodilator. It has also been studied as a possible bron- chodilator (in the treatment of asthma) and has been shown to effectively reverse methacholine-induced broncho constriction in extrinsic asthmatics.Standardized Coleus extracts containing forskolin (18% in 50 mg) find application in weight-loss programmes. (Michael T. Murray.)Studies on forskolin and some 50 derivatives of the compound indicate that the natural product is more active than the analogs prepared from it.The wild var. is known as Kaffir Potato.... coleus barbatusMany snakes are non-venomous (e.g. pythons, garter snakes, king snakes, boa constrictors) but may still in?ict painful bites and cause local swelling. Most venomous snakes belong to the viper and cobra families and are common in Asia, Africa, Australia and South America. Victims of bites may experience various effects including swelling, PARALYSIS of the bitten area, blood-clotting defects, PALPITATION, respiratory di?culty, CONVULSIONS and other neurotoxic and cardiac effects. Victims should be treated as for SHOCK – that is, kept at rest, kept warm, and given oxygen if required but nothing by mouth. The bite site should be immobilised but a TOURNIQUET must not be used. All victims require prompt transfer to a medical facility. When appropriate and available, antivenoms should be administered as soon as possible.
Similar management is appropriate for bites and stings by spiders, scorpions, sea-snakes, venomous ?sh and other marine animals and insects.
Bites and stings in the UK The adder (Vipera berus) is the only venomous snake native to Britain; it is a timid animal that bites only when provoked. Fatal cases are rare, with only 14 deaths recorded in the UK since 1876, the last of these in 1975. Adder bites may result in marked swelling, weakness, collapse, shock, and in severe cases HYPOTENSION, non-speci?c changes in the electrocardiogram and peripheral leucocytosis. Victims of adder bites should be transferred to hospital even if asymptomatic, with the affected limb being immobilised and the bite site left alone. Local incisions, suction, tourniquets, ice packs or permanganate must not be used. Hospital management may include use of a speci?c antivenom, Zagreb®.
The weever ?sh is found in the coastal waters of the British Isles, Europe, the eastern Atlantic, and the Mediterranean Sea. It possesses venomous spines in its dorsal ?n. Stings and envenomation commonly occur when an individual treads on the ?sh. The victim may experience a localised but increasing pain over two hours. As the venom is heat-labile, immersion of the affected area in water at approximately 40 °C or as hot as can be tolerated for 30 minutes should ease the pain. Cold applications will worsen the discomfort. Simple ANALGESICS and ANTIHISTAMINE DRUGS may be given.
Bees, wasps and hornets are insects of the order Hymenoptera and the females possess stinging apparatus at the end of the abdomen. Stings may cause local pain and swelling but rarely cause severe toxicity. Anaphylactic (see ANAPHYLAXIS) reactions can occur in sensitive individuals; these may be fatal. Deaths caused by upper-airway blockage as a result of stings in the mouth or neck regions are reported. In victims of stings, the stinger should be removed as quickly as possible by ?icking, scraping or pulling. The site should be cleaned. Antihistamines and cold applications may bring relief. For anaphylactic reactions ADRENALINE, by intramuscular injection, may be required.... bites and stings
Sudden death sometimes occurs in infants, usually in the ?rst year of life: this is called SUDDEN INFANT DEATH SYNDROME (SIDS) or, colloquially, cot death, the possible causes of which are an ongoing subject for research and debate.
When a person dies unexpectedly the event must be reported to a CORONER, who has the power to decide whether an AUTOPSY is necessary.... death, sudden
Habitat: Native of Mexico; found throughout India.
English: Devil's Claw, Tiger Claw.Ayurvedic: Kaakanaasikaa, Kaakaangi, Shirobal.Siddha/Tamil: Kakatundi, Thelko- dukkukai.Folk: Hathajori, Bichhuu.Action: Leaf—used in epilepsy, also applied to tuberculous glands of the neck. Fruit—anti-inflammatory. Ash of the fruit, mixed with coconut oil, is applied on burns. Seed oil— applied on abscesses and for treating itching and skin affections.
The Ayurvedic Pharmacopoeia ofIn- dia recommends the seed for arresting greying of hair.Flowers gave (several flavonoids including apigenin, luteolin, apigenin-7- O-beta-D-glucuronide, luteolin-7-O- beta-D-glucuronide, pellargonidin-3, 5-diglucoside, cyanidin-3-galactoside.The essential oil from the plant moderately inhibited passive cutaneous anaphylaxis in animals.Pentatropis microphylla W. & A. and P. spiralis Decne have also been equated with Kaakanaasaa, Kaakanaasikaa.Dosage: Dried seed—2-5 g. (API, Vol. III.)... martynia annuaIt may cause a DISULFIRAM-like reaction with alcohol; caution is similarly indicated in patients with impaired liver function or hepatic encephalopathy, and who are pregnant or breast feeding. Rare side-effects include nausea, vomiting, unpleasant taste, furred tongue and gastrointestinal disturbances; rashes, URTICARIA, and angio-oedema (see under URTICARIA); drowsiness, headache, dizziness, ATAXIA and ANAPHYLAXIS.... metronidazole
Habitat: Outer Himalaya, Assam, West Bengal; cultivated in many parts of India.
English: Tree of Sorrow, Night Jasmine, Coral Jasmine.Ayurvedic: Paarijaata, Shephaali, Shephaalikaa, Mandaara.Unani: Harasingaar.Siddha: Pavazha mattigai.Action: Leaves—bitter tonic, chola- gogue, febrifuge, anti-inflammatory, antispasmodic, hypotensive, respiratory stimulant. Used for fevers, rheumatism, obstinate sciatica.
The leaves and seeds contain iri- doid glycosides; other constituents reported from the leaves are mannitol, beta-amyrin, beta-sitosterol, hentria- contane, benzoic acid, astragalin, nico- tiflorin, oleanolic acid, nyctanthic acid, friedelin and lupeol. The seeds contain a polysaccharide glucomannan.All parts of the plant are used for allergic disorders. Alcoholic extract of the plant was found to inhibit passive cutaneous anaphylaxis (PCA) in experimental animals. The inhibition was comparable to standard drugs used for allergy and bronchial asthma.Ethanolic extract of the leaves, flowers and seeds demonstrated strong stimulation of antigen specific and non-specific immunity in mice.The 50% ethanolic extracts of the leaves, flowers, seeds and roots were found effective in treating caecal amoe- biasis caused by Entamoeba histolytica in rats. But the extracts did not exhibit direct amoebicidal activity in vitro against trophozoites of the parasite.The iridoid glucosides showed an- tileishmanial activity both in vivo and in vitro.Dosage: Leaf—10-20 ml juice. (CCRAS.)Seeds—used in diabetes, also in cutaneous diseases. Filaments— astringent and cooling; prescribed for bleeding piles and menorrhagia. Plant—toxic on the nervous system.The flowers contain flavonoids including quercetin, kaempferol, api- genin. Cardiac glucoside, nymphalin, showed sedative action in small doses.The petroleum ether extract of the plant of Nymphaea species, given at a dose of 300 mg/kg i.p. prevented necrosis of the liver tissue and promoted, to some extent, liver regeneration in CCl4-induced toxicity.Dosage: Dried flowers—3-6 g (API, Vol. III); seed—3-6 g. powder (CCRAS.).... nyctanthes arbor-tristisHabitat: Warmer parts of India, from Central Himalayas to Assam, lower hills of West Bengal; Uttar Pradesh, Andhra Pradesh, Western
Ghats from Konkan southwards to Trivandrum. Often cultivated.English: Indian Long Pepper, Joborandi.Ayurvedic: Pippali, Maagadhi, Maagadha, Maagadhaa, Maagad- hikaa, Magadhodbhavaa, Vaidehi, Upkulyaa, Pippalikam, Chapalaa, Kanaa, Krishnaa. Uushnaa, Shaun- di, Kolaa, Tikshna-tandulaa.Unani: Filfil Daraaz, Daarfilfil.Siddha/Tamil: Thippili, Arisi thippili. Thippiliver (root).Action: Fruits—used for diseases of the respiratory tract (cough, bronchitis, asthma); as sedative (in insomnia and epilepsy); as chola- gogue (in obstruction of bile duct and bladder), as emmenagogue, as digestive, appetizer and carminative (in indigestion); as general tonic and haematinic (in anaemia, chronic fevers and for improving intellect). Applied locally on muscular pains and inflammations.
Several aristolactams and dioxoa- porphines have been isolated from Indian long pepper. It also contains the long chain isobutyl amide, longamide, besides guineensine and the lignans, pluviatilol, methyl pluviatilol (farge- sin), sesamin and asarinine.Piperine is the major alkaloid of peppers.Piperine is antipyretic, hypotensive, analeptic, CNS stimulant. It has been reported to exert significant protection against CCl4-induced hepatotoxicity in mice. It improves drug availability in experimental animals, and is used for enhancing the efficacy of co- administered medicaments.Piperine enhanced bioavailability of hexobarbital, phenytoin, propranolol and theophylline. (Sharon M. Herr.) (Piperine is also a component of Piper nigrum.)N - isobutyl - deca - trans - 2 - trans - 4 - dienamide, isolated from the fruit, exhibited antitubercular property.Milk extract of the fruit effectively reduced passive cutaneous anaphylaxis in rats. It protected guinea-pigs against antigen-induced bronchospasm.In China, Piper longum oil constituents were reported to inhibit the increase in serum total cholesterol induced by triton in mice.The root powder exhibited antifer- tility activity.A related species, P. peepuloides Roxb., is known as Saamvali Peepal. It is used specifically against obstinate skin diseases and as a sialagogue.Dosage: Fruit—1-3 mg (API, Vol. IV); root—1-3 g powder. (CCRAS.)... piper longumOthers appear under their appropriate alphabetical headings: ACNE; ALBINISM; ALOPECIA; ALOPECIA AREATA; APHTHOUS ULCER; BASAL CELL CARCINOMA; BOILS (FURUNCULOSIS); BOWEN’S DISEASE; CALLOSITIES; CANDIDA; CHEILOSIS; CHEIRAPOMPHOLYX; DANDRUFF; DERMATOFIBROMA; DERMATOMYOSITIS; DERMATOPHYTES; DERMOGRAPHISM; ECTHYMA; ERYSIPELAS; ERYTHEMA; ERYTHRASMA; ERYTHRODERMA; ESCHAR; EXANTHEM; FUNGAL AND YEAST INFECTIONS; HAND, FOOT AND MOUTH DISEASE; HERPES GENITALIS; HERPES SIMPLEX; HERPES ZOSTER; IMPETIGO; INTERTRIGO; KELOID; KERATOSIS; LARVA MIGRANS; LICHEN; LUPUS; MADURA FOOT; MELANOMA; MILIARIA; MOLLUSCUM CONTAGIOSUM; MOLE; MYCOSIS FUNGOIDES; NAEVUS; ORF; PEDICULOSIS; PEMPHIGUS; PHOTOCHEMOTHERAPY; PHOTODERMATOSES; PITYRIASIS; PORPHYRIAS; PRURITUS; PSORIASIS; RINGWORM; ROSACEA; SARCOIDOSIS; SCABIES; SCLERODERMA; URTICARIA; VITILIGO; WARTS; XANTHOMATA.
Skin cancer Primary cancer is common and chronic exposure to ultraviolet light is the most important cause. BASAL CELL CARCINOMA is the most common form; squamous cell carcinoma is less common and presents as a growing, usually painless nodule which may ulcerate. Squamous cancer may spread to regional lymph glands and metastasise, unlike basal cell cancer. Occupational exposure to chemical carcinogens may cause squamous carcinoma – for example, cancer from pitch warts or the scrotal carcinoma of chimney sweeps exposed to coal dust in earlier centuries. Squamous carcinoma of the lip is associated with clay-pipe smoking.
Cancer may arise from the population of melanocytes of the skin (see MELANOCYTE; MELANOMA).
Apart from these three most frequent forms of skin cancer, various forms of cancer can arise from cells of the dermis, of which LYMPHOMA is the most important (see also MYCOSIS FUNGOIDES).
Lastly, secondary deposits from internal cancer, particularly from the breast, may metastasise to the skin.
Dermatitis and eczema These are broadly synonymous, and the terms are frequently interchangeable. Eczema is a pattern of in?ammation with many potential causes. Dermatitis is commonly used to suggest an eczema caused by external factors; it is a common pattern of in?ammation of the skin characterised by redness and swelling, vesiculation (see VESICLE), and scaling with intense itching and often exudation (weeping). Fissuring, thickening (licheni?cation – see LICHEN) and secondary bacterial infection may follow. Dermatitis can affect any part of the body. It may be genetically detemined or due to other ‘internal’ factors, such as venous HYPERTENSION in a leg, or stress. Often it is ‘external’ in origin – due to strong irritants or chemical allergens. (See also ALLERGY; ALLERGEN.) ATOPIC DERMATITIS is genetic in origin and usually begins in infancy. It may persist for years, and ASTHMA, allergic RHINITIS and conjunctivitis (see under EYE, DISORDERS OF) – ‘hay fever’ – may be associated. Atopic children tend to have multiple allergies, especially to inhaled allergens such as house-dust mite, cat and dog dander and pollens. Allergy to foods is less common but potentially more dangerous, especially if to nuts, when it can cause acute URTICARIA or even ANAPHYLAXIS. Atopic subjects are particularly prone to persistent and multiple verrucae (see WARTS) and mollusca (see MOLLUSCUM CONTAGIOSUM) and to severe HERPES SIMPLEX infections. (See also ATOPY.)
EXFOLIATE DERMATITIS (PITYRIASIS RUBRA)
Generalised exfoliation and scaling of the skin, commonly with ERYTHEMA. Drugs may cause it, or the disorder may be linked with other skin diseases such as benign dermatoses and lupus erythematosus (see under LUPUS). SUMMER POMPHOLYX is an acute vesicular eczema of the palms and soles recurring every summer. Inhaled allergens are a frequent cause. VENOUS (STASIS) DERMATITIS begins on a lower calf, often in association with PURPURA, swelling and sometimes ulceration. Chronic venous hypertension in the leg, consequent on valvular incompetence in the deep leg veins owing to previous deep vein thrombosis (see VEINS, DISEASES OF), is the usual cause. NEURODERMATITIS A pattern of well-de?ned plaques of licheni?ed eczema particularly seen on the neck, ulnar forearms or sides of the calves in subjects under emotional stress. IRRITANT CONTACT DERMATITIS Most often seen in an industrial setting (occupational dermatitis), it is due to damage by strong chemicals such as cutting oils, cement, detergents and solvents. In almost all cases the hands are most severely affected. ALLERGIC CONTACT DERMATITIS, in contrast, can affect any part of the body depending on the cause – for example, the face (cosmetics), hands (plants, occupational allergens) or soles (rubber boots). Particularly common allergens include metals (nickel and chromate), rubber addititives, and adhesives (epoxy resins).
Treatment Avoidance of irritants and contact allergens, liberal use of EMOLLIENTS, and topical application of corticosteroid creams and ointments (see CORTICOSTEROIDS) are central.... skin, diseases of
External injuries to the skin such as the sting of a nettle (‘nettle-rash’) or an insect bite cause histamine release from MAST CELLS in the skin directly. Certain drugs, especially MORPHINE, CODEINE and ASPIRIN, can have the same e?ect. In other cases, histamine release is caused by an allergic mechanism, mediated by ANTIBODIES of the immunoglobulin E (IgE) class – see IMMUNOGLOBULINS. Thus many foods, food additives and drugs (such as PENICILLIN) can cause urticaria. Massive release of histamine may affect mucous membranes – namely the tongue or throat – and can cause HYPOTENSION and anaphylactic shock (see ANAPHYLAXIS) which can occasionally be fatal.
Physical factors can cause urticaria. Heat, exercise and emotional stress may induce a singular pattern with small pinhead weals, but widespread ?ares of ERYTHEMA, activated via the AUTONOMIC NERVOUS SYSTEM (CHOLINERGIC urticaria) may also occur.
Rarely, exposure to cold may have a smiilar e?ect (‘cold urticaria’) and anaphylactic shock following a dive into cold water in winter is occasionally fatal. The diagnosis of cold urticaria can be con?rmed by applying a block of ice to the arm which quickly induces a local weal.
Transient urticaria due to rubbing or even stroking the skin is common in young adults (DERMOGRAPHISM or factitious urticaria). More prolonged deep pressure induces delayed urticaria in other subjects. IgE-mediated urticaria is part of the atopic spectrum (see ATOPY, and SKIN, DISEASES OF – Dermatitis and eczema). Allergy to peanuts is particularly dangerous in young atopic subjects. Notwithstanding the many known causes, chronic urticaria of unknown cause is common and may have an autoimmune basis (see AUTOIMMUNE DISORDERS).
Treatment Causative factors must be removed. Topical therapy is ine?ective except for the use of calamine lotion, which reduces itching by cooling the skin. Oral ANTIHISTAMINES are the mainstay of treatment and are remarkably safe. Rarely, injection of ADRENALINE is needed as emergency treatment of massive urticaria, especially if the tongue and throat are involved, following by a short course of the oral steroid, prednisolone.
Angio-oedema is a variant of urticaria where massive OEDEMA involves subcutaneous tissues rather than the skin. It may have many causes but bee and wasp stings in sensitised subjects are particularly dangerous. There is also a rare hereditary form of angio-oedema. Acute airway obstruction due to submucosal oedema of the tongue or larynx is best treated with immediate intramuscular adrenaline and antihistamine. Rarely, TRACHEOSTOMY may be life-saving. Patients who have had two or more episodes can be taught self-injection with a preloaded adrenaline syringe.... urticaria