Flashcards in Allergic skin disease Deck (71):
definition of contact dermatitis
inflammation of the skin caused by direct contact with an irritating or allergy-causing substance
irritating substance, eg acid, base, chemicals, metal salt etc.
allergy-causing substance, eg dye, oil, chemical used for fabrics, rubbers, cosmetics etc.
classification of contact dermatitis
irritant contact dermatitis
inflammatory reaction in the skin resulting from exposure to a substance that causes an eruption in most people who come into contact with it
allergic contact dermatitis
acquired sensitivity to various substances that produce inflammatory reactions in those, and only those, who have been previously exposed to the allergen
how to recognize contact dermatitis caused by acid?
brownish scab, beneath which is an ulceration that heals slowly
how to recognize contact dermatitis caused by pesticides?
large bullae, erythema
what is bromhydrosis caused by?
bacterial decomposition of apocrine sweat, producing fatty acids with distinctive offensive odors
give an example for chronic allergic contact dermatitis
lichenification caused by metal clasps
give an example for an allergen causing subacute allergic contact dermatitis
metal in a metal buckle
what may cause acute allergic contact dermatitis?
which plants may cause contact dermatitis?
name 2 examples
many, including trees, grasses, flowers, vegetables, fruits, and weeds
ex: poison ivy, mango
which allergen may cause allergic contact dermatitis in women?
what allergen may cause edema in the foreskin?
what are the differences between irritant dermatitis and allergic contact dermatitis? (6)
- acids, alkalis
- burning reaction
- everyone's affected
- no latent period
- do not use patch test!
allergic contact dermatitis:
- various substances
- allergic reaction
- only some people affected
- latent period
- patch test positive
delay between exposure to a disease-causing agent and appearance of manifestations of the disease. interval between exposure to an infectious organism or carcinogen and the clinical appearance of disease.
give 2 examples for "latent period"
after exposure to radiation, there is a latent period of 5 years, on average, before development of leukemia, and more than 20 years before development of other malignant conditions.
HIV -- latent period -- AIDS
what happens during the latent period of allergic contact dermatitis?
1) first exposure
2) skin sensitization
3) hypersensitivity develops
4) exposure (light is sufficient)
how is the patch test performed in allergic contact dermatitis?
a piece of blotting paper is soaked with suspected allergen, taped to skin for 24 to 48 h
if rash develops, the test is positive
when does reevaluation need to be done after the patch test in allergic contact dermatitis?
2 days, and again on day 4 or 5, because a positive reaction may not occur earlier
allergy skin prick test
- one of the most common methods of allergy testing
- small amount of suspected allergen is placed on skin (usually forearm, upper arm or back)
- skin is pricked to transfer the allergen to the area under skin surface
- close observation for signs of reaction (eg swelling, redness)
- several suspected allergens can be tested simultaneously
- result is obtained within 20 minutes
clinical manifestations of contact dermatitis
- contact spots with clear boundaries
- erythema or blisters
- itching or pain
- course: 1-2 weeks
- long-term repeated contact: lichenification
what is the diagnosis of contact dermatitis based on?
1. contact history
2. clinical manifestations
3. patch test
which treatments does contact dermatitis involve generally?
1. get rid of suspected allergen or irritant
2. local treatment
3. systemic treatment: antihistamines, calcium, vitamin C, corticosteroids
treatment of choice for acute dermatitis?
wet compresses of solution
what is the treatment of choice for eruptions that are limited?
topical corticosteroid cream (superior to any other local application)
definition of drug eruption
an adverse cutaneous reaction produced by ingestion, parenteral use, or local application of a drug, which may produce various morphologic patterns and types of lesions, also called drug rash
drug eruptions are most commonly caused by which drugs? (6)
- sulfa drugs
- blood serum and antitoxin
- TCM drugs
pathogenesis of drug eruptions
1) allergic reaction (most)
2) non-allergic reaction (few)
- may result from normal pharmacological effects of a drug, eg urticaria worsens with aspirin intake
features of allergic drug eruptions (6)
- occurs in a few individuals
- not related to a drug's pharmacological action and dosage
- latent period is commonly 4-20 days
- multiple lesions
- corticosteroids are effective
cross-reaction definition and example
a patient is sensitive to drug A, drug B is similar to drug A in chemical structure --> patient is also sensitive to drug B
Ex: a patient allergic to penicillin should not use cephalosporin due to risk of cross-reaction - consult department of infectious diseases for alternative drugs
classification of clinical manifestations of drug eruptions
mild drug rash and severe drug eruption
manifestations of mild drug rash
- fixed drug eruption
- urticarial drug eruption
- erythema multiforme
- purpuric drug eruption
- peripheral ring of erythema
- flatter, more purpuric, and duskier towards the center
- iris or target-like looking lesion
manifestations of severe drug eruption
- exfoliative dermatitis
- drug-induced bullosa epidermolysis
- serious erythema multiforme drug eruption
how to diagnose drug eruptions?
- history of taking medicine
- latent period
- lesions appearing abruptly
- positive drug test
how to treat drug eruptions?
- stop using suspected drug/s
- local treatment
- systemic treatment
systemic treatment of drug eruptions includes...
- supportive treatment
definition of urticaria
itchy, swollen, red wheals or patches on the skin that appear suddenly as a result of the body's adverse reaction to certain allergens. it can appear anywhere, including the face, lips, tongue, throat or ears. varies in size and can last for minutes or hours
what is urticaria also called?
definition of angioedema
- swelling similar to urticaria (hives), but occurs beneath the skin instead of on surface
- characterized by deep swelling of eyes, lips and sometimes scrotum (the most distensible tissues)
what is angioedema also called?
how frequent is urticaria?
how much percent of the population experience urticaria at some point in life?
how much percent of the population will experience urticaria alone?
how much percent of the population will experience angioedema alone?
how much percent of the population will experience urticaria and angioedema at the same time?
classification of urticaria
- evolves over days to weeks
- individual wheals last less than 24 h
- resolution within 6 weeks of onset
daily episodes of urticaria lasting longer than 6 weeks
etiology of urticaria
allergic triggers of acute urticaria
- food additives
- viral infections: hepatitis ABC, EBV
- insect bites and stings
- contactants and inhalants (including animal tander and latex)
allergic triggers of chronic urticaria
- physical factors: cold, heat, dermatographic, pressure, solar
- idiopathic: 75 % of triggers unclear
primary effector cell in urticarial reactions?
pathogenesis of urticaria
1. release of histamine from mast cells situated around capillaries
2. increased capillary permeability, small vessel dilatation -> extravasation of fluid and proteins
3. urticarial wheal formation
clinical manifestations of acute urticaria
- wheals, erythema
- duration: minutes to hours
- sudden onset and sudden disappearance
- no remaining skin changes after disappearance of lesions
clinical manifestations of severe cases of urticaria
accompanying syndromes, some being life-threatening, such as:
- respiratory: dyspnea
- GI tract: nausea, vomiting, abdominal pain
- cardiovascular system: hypotension
- edema on the skin, mucus membranes, GI tract, along with small vessel dilatation
duration of chronic urticaria
at least 6 weeks
sharply localized edema or wheal with surrounding erythematous flare occuring after seconds to minutes after the skin has been stroked
what is dermatographia also called?
what is the diagnosis of urticaria based on? (4)
1. wheals, erythema
2. sudden onset and disappearance
pharmacological options for urticaria
- calcium, vitamin c
- local treatment
antihistamines used for the treatment of urticaria (4)
- 1st generation H1 blockers
- 2nd generation H1 blockers
- tricyclic antidepressants (eg doxepin)
- combined H1 and H2 blockers
when should corticosteroids used for the treatment of urticaria? what should be avoided?
- severe acute urticaria
- long-term use
what type of solution is used to administer calcium for urticaria?
10 % calcium gluconate solution
mechanism of action of vitamin c and calcium
reduce capillary permeability
local treatment options
lotion containing menthol, phenol, and camphor has an antipruritic effect
pros and cons of 1st generation H1 blockers (diphenhydramine, hydroxyzine) for uritcaria and angioedema?
pros: rapid onset of action, inexpensive
cons: sedating, anticholinergic