The Australasian Society of Clinical Immunology and Allergy

Allergic contact dermatitis is a common skin condition that results in an itchy weeping rash, typically a few days after direct skin contact. Common causes include nickel, chemicals, plants, cosmetics, perfumes and ointments.

Allergic Contact Dermatitis is common

Allergic contact dermatitis is a common skin condition which causes an itchy weeping rash localised to the area in contact with the allergic trigger (allergen). It usually develops two or more days after contact with the allergen. It lasts as long as contact continues and for a short time (typically one to two weeks) afterwards.

Nickel metal is the most common cause of allergic contact dermatitis

In Australia, about 8% of females and 1% of males are allergic to nickel. Nickel may be found in the metal of costume jewellery, watchstraps, bra clips, jeans studs etc. The ears are often affected by wearing of non-gold earrings. The usual precipitant is piercing of the ears. Two days after contact with the metal, an itchy rash develops which may blister and weep. This rash will continue for several days or longer, if further contact with the metal continues.

Plants may also cause allergic contact dermatitis.

Some plants can trigger allergic contact dermatitis. Rashes often appear on "exposed" areas of the body after a weekend in the garden. Allergic rashes may be triggered by direct contact with the plant, or may depend on a combination of sunlight plus contact, so called "photo-contact dermatitis". Examples of plants in Australia that may cause contact dermatitis are chrysanthemums, primula, tomato plants, grevillea, English ivy and occasionally Rhus trees. Lantana or vegetables such as parsnip or celery may cause photo-contact dermatitis.

Other causes include chemicals, creams and ointments

Other common causes of allergic contact dermatitis are chemicals in rubber, leather (e.g. chrome) and dyes (e.g. paraphenylenediamine). Shoe dermatitis is common, and any one of these chemicals could be the cause.

Creams and ointments used on the skin may also cause allergic contact dermatitis.
The cause may be the base ingredient (e.g. lanolin), or the active agent (e.g. neomycin, an antibiotic). The first time the cream or ointment is applied, the rash will generally not appear for ten to fourteen days. If it is applied again, it will usually take only two days to develop. Perfumes, either on their own, or in cosmetics, can also cause allergic contact dermatitis. Even sunscreens can cause problems. 

Patch testing can identify the cause of allergic contact dermatitis

There are many causes of allergic contact dermatitis, particularly where individuals are working in industry and in contact with chemicals. If the cause of your allergic contact dermatitis is not obvious, patch testing is very helpful. This is usually performed by a dermatologist or allergist and involves placing the chemical on your back, and seeing if a reaction occurs after a few days. While it is not always easy to find cause of contact allergy, intensive patch testing usually comes up with an answer. 

Fig.1 Nickel allergy		Fig.2 Plant allergy
Allergy to a bra clip		Due to grevillea

It is important to note that information contained in this bulletin is not intended toreplace professional medical advice. Any questions regarding a medicaldiagnosis or treatment should be directed to a medical practitioner.

Content Last updated 8 February 2001