ALLERGIC CONTACT DERMATITIS
Contact Allergic dermatitis is a skin condition caused by an allergic reaction to an allergen. It differs from other types of contact dermatitis, like chemical burns and dermatitis caused by irritants like soaps.
Contact allergic dermatitis includes
cheilitis, which is specifically swollen lips and
systemic contact dermatitis, which is where you are initially sensitised to an allergen on the skin and then subsequently have allergic reactions when you come into contact with the allergen in other ways, like through ingestion or inhalation.
My favourite source of information for skin related allergies is
DermNet NZ.
Do allergens cause this type of allergy?
Yes, allergens only cause damage to people with an allergy and is safe for everyone else. In terms of food allergy, these allergens are always proteins. In contact allergies allergens are usually chemical components of fragrances, chemicals or cosmetics as well as latex and metals.
What are symptoms of contact allergy?
Contact allergies are usually Class IV delayed allergic reactions mediated by a cellular response. You can read more about the classes of allergic reactions in
10Q-3 – Allergy Questions from November. These are usually contact allergies.
Symptoms of contact allergy are typically
eczema or dermatitis under jewellery or plasters
blistering or ulceration of the skin
itching and/or red skin
swelling of skin
How can you relieve symptoms of contact allergies?
Avoidance of the allergen.
Immediately washing the area of irritation to remove the source.
Antihistamines can soothe some of the swelling and itching experienced, but soothing creams or balms can also relieve some pain.
Some contact allergens like latex can cause severe allergic reactions like anaphylaxis and this will always require administration of an epi-pen.
Why are women more frequently affected by contact allergies?
Women are more likely to wear more jewellery, wear more fragrances and use a variety of personal body products than men. This makes them much more likely to suffer from allergic contact dermatitis.
What are metal allergies?
Metal allergy is caused by an overreaction of the immune system to ions in the metal. The most common metal to be allergic to is Nickel. We have information on the
Contact Allergy Index for
Chrome,
Cobalt,
Gold,
Nickel and
Silver.
Most jewellery is a mix of different metals, so it is hard to determine which is the one you are allergic to. A dermatologist can do skin patch testing to determine which metals you need to avoid wearing.
What are latex allergies?
Latex is a product of the rubber tree,
Hevea brasiliensis, the plant has 15 associated contact allergens including
hevein,
profilin,
chitinases and
Lipid Transfer Proteins. You can read more about any of these allergens on the
Group Index Page.
Most people with a
latex allergy will only have contact allergic reactions from latex products only (like gloves, condoms and balloons), but there is a small subsection of people with this allergy who are unable to eat certain foods, usually ones which contact hevein and chitinase. This is called
Latex Food Syndrome; you can read more about it on the dedicated page.
What causes contact allergies to plants?
Lots of plants contain chemicals which can cause allergic contact dermatitis. The most commonly studied one are –
Eugenol is added to essential oils and fragrances, so can cause reactions in many different forms, it is found in lots of herbs and spices.
Urushiol is a resin found in poison ivy and sumac plants, which can cause allergic contact dermatitis. The
American Skin Association states 85% of the population of the United States are affected by urushiol in poison ivy. Plants containing urushiol are rarely found in European countries, but there are lots of plants in Asia that do, like the Chinese Lacquer Tree.
Sesquiterpenes lactones (also sometimes referred to as SQL) are found in lettuce, endives, chicory, weeds, ragweed, mugwort and artichokes.
Diallyl disulfide is a compound found in foods in the
Amaryllidaceae family of plants, this is most commonly associated with contact with garlic, but also to a lesser degree with onions, leeks and chives.
What is phytophotodermatitis?
Phytophotodermatitis (broken down mean Phyto – plant, photo – sunlight and dermatitis – skin irritation) is a condition where skin comes into contact with certain plants and is then exposed to ultraviolet light (sunlight) the skin can blister or cause a sunburn like rash. It most commonly affects people who pick, grow and process certain foods.
The main group of chemicals responsible for these reactions are called
furanocoumarins. You can read more about these chemicals on their dedicated page, which includes a food list of which foods contain them. They are commonly found in citrus fruits and fresh herbs.
If you know you have this condition and the triggers you can ensure you thoroughly wash your skin after picking fruit or herbs or avoid sunlight.
What are NOT contact allergies?
Skin reactions to
nettles are not caused by a specific allergenic protein, but by a combination of chemicals released by the plant in defence (including histamine and serotonin). Most nettle species have hair-like structures on them called 'trichomes', when these are touched, they release a combination of chemicals that cause a stinging or burning sensation on the skin.
Chemical burns are not considered to be the cause of contact allergic reactions. They are caused by strong acids or caustic chemicals and they will damage the skin of anyone who comes into contact with them and not in only certain people as is the case with contact allergic dermatitis.
Irritants do cause contact allergic dermatitis but frequent exposure to chemical irritants can cause what is sometimes called irritant contact dermatitis. It is more common in people who already have eczema and dermatitis.
Websites
References
A cross-sectional review of contact allergens in popular self-tanning products, 2024
Exploring the relationship between allergic contact dermatitis and atopic dermatitis in children: insights from a retrospective patch testing analysis, 2024
Prevalence of Type I Allergy to Latex and Type IV Allergy to Rubber Additives in Turkish Healthcare Workers, 2023
Plant Dermatitis: More Than Just Poison Ivy, 2021
Natural rubber latex allergy, 2021
A review of contact dermatitis, 2021
Mechanisms of Allergic Contact Dermatitis, 2019
Metal Allergy: Nickel, 2018
Allergic contact dermatitis: Patient management and education, 2016
Allergic contact dermatitis, 2002
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