There are several differences between allergic and irritant contact dermatitis. One is that strong chemicals can quickly irritate the skin of practically everyone, with no latent period necessary, while it usually takes at least twenty-four hours for a rash to appear after exposure in allergic dermatitis. Persons with sensitive skin or with previously existing skin problems are more easily irritated. Some chemicals can cause both irritation and allergy.
In irritant dermatitis, the severity of the reaction is directly proportional to the strength of the irritant and the susceptibility of the skin. Thus soaps and solvents are weak irritants while acids and alkalies are powerful ones. Thick and generally healthy skin is more resistant than thin, unhealthy, or fair skin.
These distinctions generally do not hold for allergic contact dermatitis. It is possible to have a mild allergy to something, but relatively brief exposure to the substance will usually produce a rash, regardless of the sensitivity of the skin. The rash may be more severe on sensitive areas such as the face, but it will develop anywhere the chemical penetrates the skin.
The early stages of a severe irritant dermatitis may be similar to an allergic dermatitis. Considerable swelling, itching, and blistering, especially with streaks and patches, normally suggest an allergic problem. A burn from a strong irritant could produce similar swelling and blistering, but the individual would probably be aware of the cause of his problem. In chronic cases of contact dermatitis, it may be quite difficult to distinguish between allergic and irritant causes. Some chemicals can cause both irritation and allergy.
In irritant dermatitis, the severity of the reaction is directly proportional to the strength of the irritant and the susceptibility of the skin. Thus soaps and solvents are weak irritants while acids and alkalies are powerful ones. Thick and generally healthy skin is more resistant than thin, unhealthy, or fair skin.
These distinctions generally do not hold for allergic contact dermatitis. It is possible to have a mild allergy to something, but relatively brief exposure to the substance will usually produce a rash, regardless of the sensitivity of the skin. The rash may be more severe on sensitive areas such as the face, but it will develop anywhere the chemical penetrates the skin.
The early stages of a severe irritant dermatitis may be similar to an allergic dermatitis. Considerable swelling, itching, and blistering, especially with streaks and patches, normally suggest an allergic problem. A burn from a strong irritant could produce similar swelling and blistering, but the individual would probably be aware of the cause of his problem. In chronic cases of contact dermatitis, it may be quite difficult to distinguish between allergic and irritant causes. Some chemicals can cause both irritation and allergy.
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