What are skin allergies?
Do you often struggle to avoid scratching? An itchy red rash, dry skin, raised bumps or swollen skin can be very uncomfortable. You might feel embarrassed and anxious, especially if you don’t know what’s causing your symptoms. Is it a skin allergy or something else?
Some common skin conditions look and feel very similar but have different causes. We’ve put together a mini resumé for these skin allergies and irritations. If you already have a diagnosis for your rash, you can go straight to the right one:
- Contact dermatitis (allergic and irritant)
- Atopic dermatitis
- Hives and angioedema
Managing a skin condition usually starts with avoiding whatever causes your symptoms or makes them worse. Your GP may suggest emollients to soothe and strengthen your skin, as well as other measures and medication. We’ll talk more about that below. First let’s look at why skin allergy happens.
Skin allergies: the root cause(s)
Allergic reactions start in your immune system when it overreacts to something harmless. This is also known as hypersensitivity. There are two main processes at play with skin allergies, depending on what type of hypersensitivity you have. Here’s how each one works.
Type I skin allergies
Many skin allergies are IgE-mediated. Your immune system sees a threat where there isn’t one. It creates Immunoglobulin E (IgE) antibodies specific to the substance or allergen. The next time you meet it you may have an allergic reaction. The antibodies trigger various cells to release chemicals such as histamine as a defensive measure. And this causes your skin reaction.
Touching some allergens can trigger hives (urticaria) or eczema (atopic dermatitis). So can eating a particular food you have an allergy to. Symptoms of Type I skin allergies usually appear within 24 hours.
Type IV skin allergies
An example of this type of hypersensitivity is contact dermatitis. This time protective white blood cells called T cells cause your skin inflammation. The first meeting with the allergen primes your immune system and sensitises you. Next time that substance touches your skin you may get a rash. Type IV allergic reactions tend to be delayed, showing themselves 12-72 hours later.
Now to those common skin conditions...here’s our first mini resumé.
1. Contact dermatitis: Skin allergy vs irritation
Contact dermatitis can be allergic or non-allergic (irritant). Hearing how quickly your rash usually starts may help your GP make the diagnosis. Allergic contact dermatitis may take a day or two to appear. The non-allergic version can flare up within minutes of an irritant touching the affected area.
Typically you get inflammation where your skin touches the substance. Symptoms can range from mild to severe and may include:
- Rash and itch
- Redness; darker skin types may have areas of deep brown or purple skin (hyperpigmentation) or ashen grey (hypopigmentation)
- Bumps or blisters, sometimes filled with clear fluid
- Skin can thicken
Itching tends to be associated with the skin allergy type of contact dermatitis. Irritants can make your skin burn or sting, and peel.
How does contact dermatitis work?
Allergic contact dermatitis involves the immune system. Irritant contact dermatitis, which is more common, does not.
Irritants damage the outer layers of your skin. The rash could happen the first time you meet certain chemicals. But everyday products like detergent can end up causing irritant contact dermatitis if you use them regularly. Jobs where your hands are often wet or you have to wash them a lot put you at greater risk.
Some irritants and allergens only cause inflammation with sun exposure. That may be why certain sunscreens give you a rash. It’s called photoallergic contact dermatitis.
Contact dermatitis: irritants and skin allergy triggers
The two conditions have different triggers. You can test for skin allergies but it’s more difficult with irritant contact dermatitis. Read more about how to get a diagnosis below.
2. Atopic dermatitis: The first (skin) allergy
This skin allergy affects 11-20% of school-aged children and 5-10% of adults in the UK. Atopic dermatitis is often the first outward sign of an overactive immune system. Babies can show symptoms and it usually starts before the age of five. There’s no single cause, instead a range of factors make it more likely. For instance, an individual or family history of certain respiratory conditions, hay fever or food allergies.
About 50% of people with severe atopic dermatitis have a faulty filaggrin gene which weakens the skin. Scientists suspect a connection. The skin barrier isn’t quite so good at protecting you. Allergens may pass through more easily. And you can lose moisture, leading to dry sensitive skin.
Common skin allergy symptoms from atopic dermatitis
Children tend to get atopic dermatitis on their cheeks, scalp, knees and elbows. For adults, the sore spots are often the face, neck and also the creases behind the ankles, knees, wrists and elbows. But severe skin allergy symptoms can affect your whole body. Here’s what to look out for:
- Dry, cracked or scaly skin
- Itchy skin, during the day and at night
- Red or brownish patches; dark brown, purplish or ashen grey on darker skin types
Scratching inflamed skin can cause bleeding. It might make the itchy feeling worse and set off what’s called the itch-scratch cycle. Over time the skin can thicken. There’s also a chance of infection. Weeping and crusting is a tell-tale sign, in which case go to your GP as soon as possible.
What triggers atopic dermatitis?
Allergens and irritants can both set off these skin allergy symptoms or make them worse. For you it might also be a combination of factors. Eczema is often linked to food allergy in very young children (not so much in adults). The rash can be slower to appear than hives. Atopic dermatitis can also be a symptom of dust mite allergy.
Particular substances linked to eczema flare-ups include chemicals, household products, toiletries and cosmetics. But also certain fabrics, dry or damp weather, getting too hot or cold, and stress. Pollen, mould spores and pets can cause skin problems too.
3. Urticaria: Skin allergy bumps
Urticaria (hives) is quite a common itchy rash. It often but not always goes with angioedema. This is swelling deep under the skin which may affect your hands, feet, face or throat.
Chronic urticaria is an itchy rash that lasts for more than six weeks. That tends to be linked to non-allergic causes like exercise, sunlight, being very hot or cold, and water. Acute urticaria goes away more quickly and it’s often a symptom of infection or allergy. The raised bumps might appear after you touch your allergy trigger. They can also be a systemic reaction to something you’ve eaten, breathed in or even been injected with.
Hives can be a warning sign of a life-threatening allergic reaction called anaphylaxis. Get medical help immediately if your heart is racing, you feel dizzy, faint or breathless, or if your throat is swelling.
Skin allergy symptoms from urticaria
Welts and wheals are other names for the itchy raised bumps that can be urticaria. Hives can be quite small or centimetres across. Typically these skin allergy symptoms look red on paler skin. After the rash goes, darker skin types may have patches of deeper colour for some time.
What triggers allergic urticaria?
Grass rash can be urticaria. It’s much less common than hay fever but some people get it from contact with grass. Otherwise, hives can be a symptom of food allergies. The itchy rash may also be a reaction to drugs, latex and insect venom – all triggers carrying a higher risk of anaphylaxis.
Is it a skin allergy? How to get a diagnosis
Finding out the exact cause – or causes – of a skin condition can be tricky. It’s often a matter of keeping a close track of your symptoms and noting down anything else happening at the same time that might be relevant.
Do you have any other allergy symptoms? Does playing sport, the weather or what you’re wearing seem to affect your skin? Toiletries, cosmetics, household products and topical medications may be a factor. Your GP will want to know about any family history of allergy or other skin conditions. They may also suggest allergy testing.
Testing for skin allergies
Patch test: Can help identify allergic contact dermatitis and other Type IV hypersensitivities. It involves taping small patches carrying the allergens to your back and checking for a reaction. It can take 48 hours or more to show.
Skin prick test: Checks whether a Type I allergy could be giving you eczema or hives. The allergist or allergy nurse puts drops of liquid containing different allergens onto your skin and pricks it gently. An itchy bump may appear within the next 15-20 minutes. To confirm a food allergy you may need a blood test or an oral food challenge too.
Allergy blood test: Can be more reliable and less uncomfortable than a skin prick test if you already have a rash or itchy skin. Allergy blood tests look for IgE antibodies in your blood and show what you could be allergic to.
Challenges: Exposes you deliberately to a food or drug allergen to see if you have an allergic reaction. It’s done under expert supervision in a medical setting.
Five practical tips for skin allergies and irritations
Your GP will come up with a management and treatment plan for you. Exactly what that involves will depend on your particular skin condition and what’s causing it. But it’s likely to start with avoiding your allergy triggers or skin irritants. Or both. If you have inflamed or sensitive skin, these measures may help:
- Use gloves or other protective clothing whenever necessary
- Buy cotton underwear and nightwear; they’re gentle on sensitive skin
- Wash new clothes before you wear them and avoid fabrics that might be scratchy
- Choose personal care and household products that are perfume-free and hypoallergenic
- Keep your skin moisturised with emollients
Moisturising ointments, lotions and creams can act as a protective layer on top of your skin and seal in water. Your GP will know the right one for your skin allergy or irritation and how often to use it. That may include after your shower or bath. Smooth it into your skin; don’t rub as that could fire up your itch.
Some treatment options
It’s often hard to avoid scratching but doing so can make hives and eczema symptoms a lot worse. There are home remedies you could try; cold compresses, calamine lotion and oatmeal baths.
The right symptom-relieving medication will depend on your skin condition. Treatment for hives often starts with antihistamine. For contact dermatitis or atopic dermatitis the first choice tends to be an anti-inflammatory corticosteroid cream or ointment.
Severe skin allergy symptoms may need other treatment. Your GP might occasionally prescribe oral steroids for atopic dermatitis flare-ups or urticaria. But it will only be for very short periods of time because of the risk of side effects. There are also biologic injections for atopic dermatitis available on prescription. Over-the-counter oral antihistamines or steroids may help very itchy skin from contact dermatitis.
Topical immunomodulators can treat inflammation too. Severe eczema may call for combining this medication or a topical steroid with wet-wrap therapy. Meanwhile, another possible treatment is light therapy (phototherapy).
Ask your GP to explain the treatment options to you.