Find A DoctorAllergic reaction hives
If you’ve noticed itchy or raised bumps appearing on your skin, only to disappear within 24 hours, you may have experienced allergic reaction hives, or immunologic contact urticaria. Hives can develop when the body releases histamine. Histamine is an inflammatory chemical that protects you from infection. But sometimes your body releases histamine when there’s no real threat. This happens during an allergic reaction.
Allergic reaction hives can appear on any part of the body and cover both large and small areas of skin – depending on the severity of the reaction. Usually, the longer a person is in contact with an allergen the more severe their hives are.
Healthcare providers tend to treat allergic reaction hives with antihistamines. But treatments can differ depending on severity. Anything that you’re sensitized to has the potential to cause hives. But if you have an allergy, avoiding your allergen can be an effective way to prevent hives and other allergy symptoms from developing.
What do allergic reaction hives look like?
Allergic reaction hives (also referred to as welts or wheals) can look the same as other types of hives with different causes. When hives symptoms develop you may feel an itchy, stinging or burning sensation around the rash. Hives can appear in batches and may show as smooth raised marks of different shapes and sizes.
Hives are not the
only skin allergy
If you have paler skin, you may notice your allergic hives rash is slightly red or pink. But if your skin is darker, the hives may have a similar appearance to your unaffected skin. Consequently, making them more difficult to spot.
Hives and angioedema can present at the same time, angioedema is a type of swelling that can block the airways, preventing a person from breathing. Angioedema is a symptom of anaphylaxis, which is a medical emergency.
Can hives be serious?
Hives in some instances can be a sign of anaphylaxis. Anaphylaxis is a severe allergic reaction that affects your whole body (systemic) and can be life threatening. For this reason, it always requires urgent medical treatment, usually with an epinephrine.
Signs and symptoms of anaphylaxis include:
- Pollens from trees, grasses or weeds
- Waste particles from house dust mites
- Molds
- Certain foods such as nuts, dairy, shellfish
- Pet dander
- Insect stings
What to do if your hives are a symptom of anaphylaxis
People at risk of anaphylaxis are usually prescribed epinephrine. This emergency medication comes in the form of an auto-injector and you’ll receive training on how to use the device from your healthcare provider.
Keep two auto-injectors with you at all times. Use one immediately when you experience symptoms of anaphylaxis and seek immediate medical attention or go to the emergency room. You may feel better after the first dose of epinephrine but there’s a risk of developing a second delayed reaction.
What you need to know
about anaphylaxis
Types of allergic reaction hives
There are many types of allergic reaction hives. These include:
Contact urticaria
Contact urticaria can be caused by both allergens and irritants. Sometimes though, the exact cause is unknown. When a person has allergic contact urticaria, they’ve encountered an allergen and hives are a symptom of their immune system responding to that allergen.
Allergens that can cause contact urticaria include, but are not limited to: foods, such as nuts, seafood, wheat, milk, eggs and medications, such as penicillin or anti-inflammatory drugs
More often though, people tend to experience contact urticaria through irritants rather than allergens. Symptoms of contact urticaria caused by irritants are typically less severe than those caused by allergens.
Confusingly, there is a lot of overlap between irritants and allergens that can cause contact urticaria. For example, some animal products, foods, medications and plants can all be irritants as well as allergens. So, for this reason if you do experience contact urticaria, you should always speak with your healthcare provider who can check if you have an allergy or not.
Solar urticaria (solar hives)
Solar urticaria is a rare allergic reaction to sunlight where hives can develop within minutes of sun exposure. Other allergy symptoms such as nausea and shortness of breath can happen if you’ve been in the sun for a long time or had a large area of skin exposed.
Wearing thin or white clothing sometimes isn’t enough to prevent sun exposure; you should aim to wear darker clothing. And apply a broad-spectrum sunscreen to block both UVA and UVB rays.
Cholinergic urticaria
Cholinergic urticaria is a type of hives that develops when your body temperature is high enough for you to sweat. Researchers don't fully understand why cholinergic urticaria happens but think that it involves the release of histamine.
Need help managing hives or other allergy symptoms? Maybe it’s time to see an allergy specialist near you.
Cholinergic urticaria can sometimes be confused with heat urticaria. Heat urticaria is a very rare type of physical urticaria where exposure to medium heat causes hives. For example, if you submerge your hand in warm water, hives may develop on your hand. With cholinergic urticaria, you must begin to sweat or the sweating reflex needs to be activated for you to develop hives.
Allergic reaction hives diagnosis and treatment
Diagnosing hives, or more accurately allergic reaction hives, may require several tests. These could include blood tests to rule out infection or other skin rashes caused by the immune system. Your healthcare provider may also ask questions about what you were doing before the hives appeared. This helps them determine if your hives were a symptom of an allergic reaction.
When treating allergic reaction hives, the aim is to control symptoms and avoid future episodes of hives. So, once a healthcare provider diagnoses the cause of allergic reaction hives, they’ll create a treatment plan to suit your needs. For instance, they’re likely to suggest avoidance strategies to help reduce your exposure to the allergen, and taking antihistamines when this isn’t possible.
Treatment for more severe allergic reaction hives may include corticosteroids. Like antihistamines these aim to reduce inflammation and itching.
Where do allergic reaction hives appear?
Allergic reaction hives can affect small or large areas of skin anywhere on your body. They also tend to develop first where you've encountered the allergen. Hives, like other allergy symptoms, may get worse if you're repeatedly in contact with your allergen.
Pictures of hives on different parts of the body
Can hives develop with infection?
Yes, you could develop hives from infection. When this happens you usually have chronic hives – hives that last for 6 weeks or more. Bacterial infections that have been linked to hives include Helicobacter pylori, which commonly causes stomach ulcers. Viral infections can also cause hives, such as hepatitis and norovirus. Researchers are still understanding why some bacteria and viruses cause hives but think it could be due to how a person’s immune system responds to the infection.
What is chronic urticaria (chronic hives)?
Chronic hives last for 6 weeks or more and are usually linked with infection and autoimmune conditions, for example thyroid disease. Hives caused by allergies are usually acute hives and tend to go away within 24 hours – providing the person is no longer in contact with the allergen. Or has received treatment for their allergic response.
Summary
Allergic reaction hives look like reddish pink bumps on pale skin. They may be more difficult to spot on darker skin as the bumps tend to be a similar color. In both skin types, hives appear in raised batches.
Doctors tend to treat allergic reaction hives with antihistamines but there are other medications for more severe cases. Anaphylaxis is a life-threatening systemic allergic reaction that requires urgent medical treatment, usually with epinephrine.
Allergic reaction hives are a type of acute urticaria. The bumps tend only to last for 24 hours, providing a person has received treatment or is no longer in contact with their allergen. Chronic hives last longer than 6 weeks and are typically a symptom of an infection or an autoimmune condition.
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