Contact allergy: description
Contact allergy is an exaggerated reaction of the immune system to a certain substance with which the skin has come into contact. The affected skin areas react allergically, they become inflamed and itchy.
Contact allergy is relatively common. About eight percent of adults in Germany are affected – women more often than men.
Contact allergy is a so-called allergy of the delayed type IV or late type. It is characterized by the fact that the symptoms only appear 24 hours to three days after contact with the allergy trigger (allergen). Nickel is the most common contact allergen. However, other metals, plants or fragrances can also trigger a contact allergy.
What happens during an allergy?
Contact allergy: symptoms
A contact allergy manifests itself in changes on the skin that appear about one to three days after skin contact with the allergen. The following symptoms may appear at the sites where the skin came into contact with the allergenic substance:
- Reddening of the skin (erythema)
- swelling (angioedema)
- oozing vesicles
- wheal formation
- crusting or scaling
- itching or burning
If skin contact is prolonged, chronic contact dermatitis develops: The skin becomes coarser, cornified, and forms ridges (lichenification).
Contact allergy: causes and risk factors
Any substance found in the environment can theoretically cause contact allergy. However, particularly common contact allergens are:
- Metals (e.g., nickel in jewelry, zippers, buttons)
- Fragrances (e.g. in perfumes, soaps, cosmetics)
- Preservatives
- plants (e.g. chamomile, mugwort, arnica)
- essential oils (e.g. lemon or peppermint oil)
- cleaning agents (e.g. softeners)
- latex (e.g. as latex gloves)
Contact allergy: examinations and diagnosis
To be able to diagnose “contact allergy”, the doctor must first take the patient’s medical history (anamnesis). To do this, he asks the patient, for example:
- When did the symptoms first appear?
- Are the symptoms limited to one area of the skin?
- Is there anything that can alleviate the symptoms, for example, avoiding certain items of clothing or jewelry?
- Do you have any known allergies?
The doctor then examines the corresponding skin areas in more detail. He then performs an epicutaneous test (patch test) to identify possible allergens. A sample of the allergenic substances in question is applied separately to the patient’s back and covered with patches. After one to two days, the physician removes the plasters and looks to see whether one of the applied substances has actually caused a local hypersensitivity reaction of the skin (redness, wheal formation).
Exclusion: Toxic contact dermatitis
Contact allergy: treatment
A contact allergy cannot be completely cured. The sensitization of the immune system against the respective allergen usually remains for life. However, one can try to avoid skin contact with the allergen. If this is not (always) possible, one can at least alleviate the symptoms of the contact allergy with medication or UV therapy. In addition, affected skin areas should be well cleaned to promote the healing process. Moisturizing and skin care products help the skin to rebuild. Rehydrating creams, oils or baths are recommended.
Medication
If necessary, an ointment containing cortisone may be applied to the skin. Cortisone inhibits the excessive immune response and thus reduces the inflammatory reaction in the skin. The type of cortisone and duration of use must be carefully weighed by the physician against the known side effects of treatment: Cortisone can, among other things, make the skin thinner and blotchy if used for a long time. Therefore, preparations containing cortisone should only be applied for a short time and to small areas of the skin.
In the case of chronic hand eczema, the doctor may prescribe the active substance alitretinoin (similar structure to vitamin A) to be taken. It has an anti-inflammatory effect and regulates the immune system. Because of its fertility-damaging effect, women of childbearing age must ensure effective contraception during treatment and for a further four weeks afterwards.
UV therapy
In the case of chronic eczema (especially chronic hand eczema), UV therapy (a form of light therapy) can help. Either irradiation with UV-B light (UVB therapy) or irradiation with UV-A light in combination with the active substance psoralen (PUVA therapy) is used. Psoralen can be ingested or applied locally to the skin.
Avoid allergen contact
People with a contact allergy should avoid the allergenic substance as much as possible. If necessary, the skin can be protected with special clothing and gloves, for example if one is allergic to cleaning agents. Sometimes, however, certain activities must be avoided altogether, for example at work.
Contact allergy: course of the disease and prognosis
A contact allergy usually persists for a lifetime. Depending on which allergens the affected person reacts to, how strongly the immune system has been sensitized and how long the contact with the allergenic substance lasts, the symptoms can be milder or more severe. If the triggering substances are avoided, the symptoms often disappear on their own within two to three weeks.
If a contact allergy persists for a long time, the affected skin areas can become infected by fungi or bacteria. The skin then becomes warm, very red or swollen and painful. An infection is treated with antimycotics (against fungi) or antibiotics (against bacteria), depending on the pathogen.
Contact allergy: prevention possible?
Contact allergy usually occurs without precursors, there is no prophylaxis. However, it is possible to reduce the risk of allergies in general. For example, it is known that breastfed babies suffer less frequently from allergies. If children grow up in households with animals, this also reduces their risk of developing allergies such as contact allergy.
