SkinTECH

Who should have a patch test?

 

• Any patient suspected of having an allergic contact dermatitis.

• All patients with facial eczema

• All patients with hand dermatitis

• All patients with discoid eczema

• Any patient whose eczema does not clear within a month.

• Patients with recurrent eczema.

 

When to suspect an allergic contact dermatitis.

 

• When there is a history of rash following contact with a substance eg. a rash on the lips following application of lipstick, a rash on the feet following the wearing of new shoes, a rash on the face after applying a new cosmetic etc.

• When the rash is localised to the area of application of the suspected agent.

• When certain parts of the body are involved, eg. eyelids, hands, feet, face, fingertips, ear lobes, writsts.

 

 

What chemicals should one test for?

 

It is usual to start with a standard series - usually made up around 30 of the most common chemicals that are capable of causing a rash. Many countries have their own standard series. In South Africa, such a series has not been developed and the usual route is to start with the European Standard Series (28 chemicals) or the International Series (52 chemicals).

How does one interpret a positive result?

 

A positive result is indicated by various degrees of redness, blistering and elevation of the skin. A reading plate is available with pictures showing degrees of positivity. 

 

 

What happens if a positive result is found?

 

The patient is informed that he/she is allergic to that particular chemical. A printout can be obtained from the Chemotehcniques website listing the substances which contain the offending chemical. The patient is asked to avoid contact with these substances. 

 

 

Is this information freely available?

 

Yes. All you have to do is to register with the Chemotechinques website (for free) and download the necessary information.

 

 

 

Should a patch test be performed on Atopic patients (patients with atopic dermatitis)

 

Although atopic dermatitis is considered to be an endogenous eczema (eczema of unknown origin), it is possible for atopic patients to develop a superimposed contact dermatitis, sometimes even from the medication used to treat the condition. Patch testing is therefore useful in selected patients with atopic dermatitis.