What is an epicutaneous test?
The epicutaneous test is a skin test for the diagnosis of contact allergies (allergic contact dermatitis or allergic contact dermatitis). They are caused by prolonged direct skin contact with the triggering substance (allergen, e.g. nickel-containing necklace). Because the allergic reaction occurs with a time delay, physicians speak of a late-type allergy (type IV).
When do you perform an epicutaneous test?
Doctors perform an epicutaneous test when they suspect or want to rule out a contact allergy in someone. This can be the case, for example, with recurring unclear skin changes.
The epicutaneous test can be used to investigate the following allergies, for example:
- Nickel allergy and allergies to other metals
- Latex allergy
- Allergies to fragrances or dyes
- Contact allergies to various plants
What is done in an epicutaneous test?
In an epicutaneous test, the examiner usually sticks possible allergy triggers (allergens) on the patient’s back, alternatively on the upper arm or thigh. For this purpose, he usually mixes the allergen with Vaseline (carrier substance). This preparation is then applied to test flaps, foils or in aluminum chambers and taped down.
The patch usually stays on the skin for two days. After the two days, the doctor checks whether there are any allergic skin reactions in one or more places: The skin is red and swollen, itchy or oozing, and small blisters may have formed.
What are the risks of an epicutaneous test?
The epicutaneous test is a relatively safe examination. Nevertheless, there are also risks and side effects. At the tested skin site
- heat and moisture accumulation or the adhesive strips may irritate the skin,
- the test reaction may last for a long time (normally allergic reactions disappear within two weeks),
After an epicutaneous test, side effects affecting other parts of the body or the whole body are also possible. For example, an existing rash may worsen or a healed rash may flare up again.
Rarely, people develop a new hypersensitivity to one of the test allergens. Doctors then speak of a primary sensitization. To minimize this risk, the physician carefully considers which substances to use in the epicutaneous test.
Also rare, but still possible, are life-threatening allergic reactions (anaphylactic shock).
If you suddenly notice complaints such as tingling on the body, shortness of breath, abdominal cramps or dizziness during an epicutaneous test, call the emergency services immediately.
What do I need to be aware of during the epicutaneous test?
As long as you have applied the patches for the epicutaneous test, you should not shower, do any sports and avoid heavy sweating.
In some circumstances, physicians cannot order an epicutaneous test. This is the case, for example, if patients suffer from an extensive skin rash on the body or another acute illness.
Also, if the skin has recently been treated with “cortisone”, an epicutaneous test is not advisable: it may suppress the allergic reaction and falsify the result. You can read more about such contraindications in our article “Allergy test”.
