How a skin patch test is used to determine the cause of irritant contact eczema ?
A skin patch test is used to determine cause of certain types of eczema. Typically, this is done when the underlying cause of eczema flare-ups is likely to be one or more irritants the patient is exposed to – a condition known as irritant contact eczema.
A skin patch test will help identify the specific substance that is triggering the eczema symptoms. For example, the doctor will be able to find out whether the allergen exists in one of the cosmetic products being used by the patient or if it is something found in a clothing item.
Basically, the skin patch test involves placing the suspected irritant in contact with the skin for a certain period of time and then examining the skin to see if there is any allergic response. The irritant is held in place by using an adhesive patch. To provide a point of comparison, another adhesive patch, which does not contain any allergic substance, is also placed against the skin.
These adhesive patches may be left in place for one or two days. They are then removed and the skin is examined. If the skin shows itchiness, becomes inflamed or reddened, it is highly likely that the irritant used in the patch is a substance the patient is allergic to.
Skin patch testing is done by a dermatologist or other skin specialist. If the patient had initially consulted a general practitioner, the later will usually refer the patient to a specialist for testing. Testing becomes necessary when the patient’s eczema is deemed to be the result of an allergic response.
The testing process usually spans a few days. On the first day, the dermatologist may apply small amounts of a variety of substances to the patient’s upper back using patches. Thirty or more substances may be chosen for testing. Non-allergic tape is used to fix the patches on to the skin.
The patches stay on the skin for a couple of days following which the patient must come back to the specialist’s office. The patches are then removed and the skin surface is closely examined for the presence of any allergic reactions.
Quite often allergic reactions take place with a time lag. To account for this delay, the doctor may ask the patient to come back for another examination two days after the patches have been removed.
A wide variety of substances are tested during the process. Most of them are additives used in everyday products like household cleaners, clothing materials, soaps, cosmetic products, leathers and more. Examples of additives include quaternium-15, imidazolidinyl urea, ethylenediamine, rosin, formladehyde, rubber accelerators, nickel, balsam of Peru, P-tert butylphenol, plants, chrome, lanolin (also called wool alcohol), neomycin, clioquinol, paraphenylenediame, benzocaine, formaldehyde resin, fragrances, quaternium-15, paraben mix, cobalt, imidazolidinyl urea and epoxy resin.
These substances form a standard battery of patches and are often used by dermatologists. Other possible irritants may be added to the above – for example, a chemical that is used at the patient’s workplace or a specific cosmetic product he is using.
It is important to maintain a clean, dry skin while going for the initial visit to the dermatologist. This should be maintained throughout the duration of the skin patch test, till the doctor confirms that the procedure is complete. In most cases, the patient will be advised to restrict himself to a sponge bath instead of taking a regular shower or bath. It is also necessary to avoid doing anything that might cause excessive sweating. This is particularly important in hot, humid summer climates. This may mean curtailing physical activity including sports, jogging, etc for a few days.
Skin patch tests can uncover the cause of irritant contact eczema. It is, however, not of use in determining the cause of other kinds of eczema such as those caused by food. A skilled dermatologist can usually uncover the irritant/s and thus help deal with the eczema symptoms.