Skin allergy: consult a doctor by instant messaging

Skin allergy: why and when to see a doctor?

A skin allergy (or allergic reaction) is caused by an abnormal response of the immune system to substances that are normally harmless. In some cases, an allergy can be potentially life-threatening: this is known as an anaphylactic reaction. A skin allergy generally presents as a rash, often accompanied by itching. An allergy can also cause sneezing, watery eyes and a runny nose. It can be worthwhile carrying out skin tests to identify the substance responsible for the allergic reaction.

Skin allergy: immune mechanism and triggering factors

Typically, the immune system — made up of white blood cells, antibodies, proteins, mast cells and other substances — defends the body against foreign substances (antigens). Nevertheless, some people can be more sensitive and react excessively when exposed to certain allergenic substances. These allergens can be present at several levels:
   • In the environment (wind, cold, rain, sun, etc.);
   • In the environment (wind, cold, rain, sun, etc.);
   • Or even in medications that are normally harmless.
People can also be allergic to a single product or to several agents. It is estimated that in the United States, around a third of people are affected by allergies. Finally, allergens are transmitted by contact with the eyes or skin, or when they are inhaled, injected or ingested. A skin allergy can therefore occur in different ways:
   • The allergy can be seasonal (like hay fever) following exposure to certain substances: pollen, ragweed, grasses…
   • Triggered after taking a medication (drug allergy);
   • Caused by certain foods (food allergy);
   • Triggered by mould, animal hair or the inhalation of dust
   • By contact with certain substances (latex);
   • Or by insect bites or stings (angioedema, anaphylactic reactions)
Generally, when the immune defences are exposed to an allergen for the first time, they produce a specific antibody called immunoglobulin. The immunoglobulin then binds to certain white blood cells (basophils) present in the blood, and to other cells (mast cells) present in the tissues. During the first exposure to the allergen, the person may become sensitised, without necessarily showing any symptoms. But when the person is exposed to this allergen again, the mast cells and basophils carrying immunoglobulins on their surface start releasing substances (prostaglandins, histamine, leukotrienes) responsible for inflammation or swelling of the surrounding tissue. These substances trigger a cascade of allergic reactions, causing irritation and damage to the skin.

What causes a skin allergy?

Many environmental and genetic factors can combine to cause allergies. Doctors believe that several genes are involved, since allergies tend to run in families, and also because specific mutations have been observed in people who suffer from allergies. As for the environmental factors that increase the risk of developing allergies, they include:
   • Diet;
   • Repeated exposure to allergens (foreign substances);
   • Pollutants (exhaust fumes, cigarette smoke…).
On the other hand, being exposed during childhood to various bacteria and viruses can help strengthen the immune system. This can also help prevent the development of allergies, by helping it learn to respond to allergens in a non-dangerous way. So it's a rather counter-intuitive idea, yet a real one: an environment that is too clean, or one that disproportionately limits a child's exposure to bacteria and viruses, can make the child more prone to allergies later on. Generally, exposure to micro-organisms is limited in very clean indoor environments and in small families. The use of antibiotics at a very young age also increases the risk of developing allergies. Finally, the number of micro-organisms present on the skin, in the airways or in the digestive tract varies from person to person. Depending on the micro-organisms present, a person will or will not develop one or more specific allergic reactions. The most common allergens are:
   • Animal dander (fur, skin);
   • Mould;
   • Pollen;
   • Dust mite droppings. Dust mites live in the dust that accumulates in bedding, carpets, soft toys and upholstery fabrics;
   • Certain foods;
   • Certain medications;
   • Insect venom;
   • Latex;
   • Cleaning products, household chemicals, perfumes…

Symptoms of a skin allergy

Most of the time, allergic reactions are not very severe. They mainly present as:
   • Watery eyes;
   • A runny nose;
   • Itching, in particular itchy eyes;
   • Itchy skin;
   • Skin rashes, red patches;
   • Hives (urticaria);
   • Eczema (dermatitis);
   • Swelling (oedema);
   • Sneezing.
Hives present as small, swollen, slightly raised red areas (wheals), the centre of which is generally pale. When the swelling affects larger areas beneath the skin, it is known as angioedema. This swelling can, for example, be caused by an insect sting and can be very serious. Angioedema is caused by fluid leaking from the blood vessels. Allergies can also trigger asthma attacks. Other allergies can be potentially life-threatening, such as anaphylactic shock, characterised by constriction and narrowing of the airways. Breathing can become disrupted and wheezy, and the mucous membranes lining the airways and throat swell up. Blood vessels can also dilate and widen, leading to a potentially dangerous drop in blood pressure.

See a dermatologist if you have a skin allergy

The best treatment remains prevention, by avoiding allergens. It is obviously advisable to see a dermatologist (or a general practitioner) to identify potential allergens or triggering factors. Skin tests can be carried out if necessary. Online consultation offers the benefit of same-day care, without an appointment. As for the possible treatments, they include:
   • Antihistamines;
   • Corticosteroids, a specific cream;
   • Mast cell stabilisers;
   • Immunotherapy targeting the identified allergens;
   • Emergency treatment in the event of a severe allergy.
Antihistamines are often enough for mild symptoms. When they are not effective, other medications can help (corticosteroids, mast cell stabilisers). Non-steroidal anti-inflammatory drugs (NSAIDs), however, are not recommended, except to treat conjunctivitis in the form of eye drops. Moisturising creams will also have no effect on a skin allergy. Above all, if in doubt or if you have severe respiratory symptoms, seek emergency care, as some allergies can be very dangerous to your health. If it is a simple allergy, an online dermatologist can give you advice to relieve your symptoms and prescribe you a treatment.