How do you tell if a rash is an allergic reaction
Allergies
Overview
Allergies occur when your immune system reacts to a foreign substance such as pollen, bee venom or pet dander or a food that doesn't cause a reaction in most people.
Your immune system produces substances known as antibodies. When you have allergies, your immune system makes antibodies that identify a particular allergen as harmful, even though it isn't. When you come into contact with the allergen, your immune system's reaction can inflame your skin, sinuses, airways or digestive system.
The severity of allergies varies from person to person and can range from minor irritation to anaphylaxis a potentially life-threatening emergency. While most allergies can't be cured, treatments can help relieve your allergy symptoms.
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Symptoms
Allergy symptoms, which depend on the substance involved, can affect your airways, sinuses and nasal passages, skin, and digestive system. Allergic reactions can range from mild to severe. In some severe cases, allergies can trigger a life-threatening reaction known as anaphylaxis.
Hay fever, also called allergic rhinitis, can cause:
- Sneezing
- Itching of the nose, eyes or roof of the mouth
- Runny, stuffy nose
- Watery, red or swollen eyes (conjunctivitis)
A food allergy can cause:
- Tingling in the mouth
- Swelling of the lips, tongue, face or throat
- Hives
- Anaphylaxis
An insect sting allergy can cause:
- A large area of swelling (edema) at the sting site
- Itching or hives all over the body
- Cough, chest tightness, wheezing or shortness of breath
- Anaphylaxis
A drug allergy can cause:
- Hives
- Itchy skin
- Rash
- Facial swelling
- Wheezing
- Anaphylaxis
Atopic dermatitis, an allergic skin condition also called eczema, can cause skin to:
- Itch
- Redden
- Flake or peel
Anaphylaxis
Some types of allergies, including allergies to foods and insect stings, can trigger a severe reaction known as anaphylaxis. A life-threatening medical emergency, anaphylaxis can cause you to go into shock. Signs and symptoms of anaphylaxis include:
- Loss of consciousness
- A drop in blood pressure
- Severe shortness of breath
- Skin rash
- Lightheadedness
- A rapid, weak pulse
- Nausea and vomiting
When to see a doctor
You might see your health care provider if you have symptoms you think are caused by an allergy, and nonprescription allergy medications don't provide enough relief. If you have symptoms after starting a new medication, call the provider who prescribed it right away.
For a severe allergic reaction (anaphylaxis), call 911 or your local emergency number or seek emergency medical help. If you carry an epinephrine auto-injector (Auvi-Q, EpiPen, others), give yourself a shot right away.
Even if your symptoms improve after an epinephrine injection, you should go to the emergency department to make sure symptoms don't return when the effects of the injection wear off.
If you've had a severe allergy attack or any signs and symptoms of anaphylaxis in the past, make an appointment to see your health care provider. Evaluation, diagnosis and long-term management of anaphylaxis are complicated, so you'll probably need to see a provider who specializes in allergies and immunology.
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Causes
An allergy starts when your immune system mistakes a normally harmless substance for a dangerous invader. The immune system then produces antibodies that remain on the alert for that particular allergen. When you're exposed to the allergen again, these antibodies can release a number of immune system chemicals, such as histamine, that cause allergy symptoms.
Common allergy triggers include:
- Airborne allergens, such as pollen, animal dander, dust mites and mold
- Certain foods, particularly peanuts, tree nuts, wheat, soy, fish, shellfish, eggs and milk
- Insect stings, such as from a bee or wasp
- Medications, particularly penicillin or penicillin-based antibiotics
- Latex or other substances you touch, which can cause allergic skin reactions
Risk factors
You might be more likely to develop an allergy if you:
- Have a family history of asthma or allergies, such as hay fever, hives or eczema
- Are a child
- Have asthma or another allergic condition
Complications
Having an allergy increases your risk of certain other medical problems, including:
- Anaphylaxis. If you have severe allergies, you're at increased risk of this serious allergy-induced reaction. Foods, medications and insect stings are the most common triggers of anaphylaxis.
- Asthma. If you have an allergy, you're more likely to have asthma an immune system reaction that affects the airways and breathing. In many cases, asthma is triggered by exposure to an allergen in the environment (allergy-induced asthma).
- Sinusitis and infections of the ears or lungs. Your risk of getting these conditions is higher if you have hay fever or asthma.
Prevention
Preventing allergic reactions depends on the type of allergy you have. General measures include the following:
- Avoid known triggers. Even if you're treating your allergy symptoms, try to avoid triggers. If, for instance, you're allergic to pollen, stay inside with windows and doors closed when pollen is high. If you're allergic to dust mites, dust and vacuum and wash bedding often.
- Keep a diary. When trying to identify what causes or worsens your allergic symptoms, track your activities and what you eat, when symptoms occur and what seems to help. This may help you and your provider identify triggers.
- Wear a medical alert bracelet. If you've had a severe allergic reaction, a medical alert bracelet (or necklace) lets others know that you have a serious allergy in case you have a reaction and you're unable to communicate.
Aug. 05, 2022
What Is an Allergic Reaction?
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An allergic reaction happens when your immune system defends against substances that otherwise wouldnt pose a threat to your body. Common allergens include pollen, mold, and certain foods.
Your immune system is responsible for defending the body against bacteria and viruses. In some cases, your immune system will defend against substances that typically dont pose a threat to the human body. Some of these substances are known as allergens, and when your body reacts to them, it causes an allergic reaction.
You can have an allergic reaction after inhaling, eating, or touching an allergen. Doctors can also use allergens to diagnose allergies and can even inject them into your body as a form of treatment.
The American College of Allergy, Asthma & Immunology (ACAAI) reports that over 50 million people in the United States have some type of allergy.
Doctors dont know why some people experience allergies. Allergies appear to run in families, which means they can be inherited. If you have a close family member who has allergies, youre at greater risk for developing them.
The reasons why allergies develop are unclear, but some substances are known to commonly cause an allergic reaction. People who have allergies are typically allergic to one or more of the following:
The symptoms of an allergic reaction can vary from mild to severe. If you become exposed to an allergen for the first time, your symptoms may be mild. These symptoms may get worse if you repeatedly come into contact with the allergen.
Mild reaction
Symptoms of a mild allergic reaction can include:
Severe reaction
Severe allergic reactions (usually to foods, insect stings, and medications) can cause the following symptoms:
A severe and sudden allergic reaction known as anaphylaxis can develop just seconds after exposure to an allergen. This type of reaction results in life threatening symptoms, including:
If you experience anaphylaxis, seek immediate emergency help. Without treatment, anaphylaxis can result in death.
A primary care physician or an allergist can diagnose allergic reactions.
If you experience symptoms of an allergic reaction, the doctor will perform an exam and ask you about your health history. If your allergic reactions are severe, they may ask you to keep a journal that details your symptoms and the substances that appear to cause them.
The doctor may want to order tests to determine whats causing your allergy. The most commonly ordered types of allergy tests are:
- skin tests
- challenge (elimination-type) tests
- blood tests
Skin test
A skin test involves applying a small amount of a suspected allergen to the skin and watching for a reaction. The substance may be:
- taped to the skin (patch test)
- applied via a small prick to the skin (skin prick test)
- injected just under the skin (intradermal test)
A skin test is most valuable for diagnosing:
Challenge (elimination-type) test
Challenge testing is useful in diagnosing food allergies. It involves removing a food from your diet for several weeks and carefully watching for symptoms when you eat the food again.
Blood test
A blood test allows the doctor to check your blood for antibodies against a possible allergen. An antibody is a protein your body produces to fight harmful substances.
Blood tests are an option when skin testing isnt helpful or possible.
If you need help finding an Allergist and Immunologist, then check out our FindCare tool here.
If you experience an allergic reaction and you dont know whats causing it, you may need to see a doctor to determine which substances youre allergic to. If you have a known allergy and experience symptoms, you may not need to seek medical care if your symptoms are mild.
In most cases, over-the-counter antihistamines, such as diphenhydramine (Benadryl), can be effective in controlling mild allergic reactions.
Shop for over-the-counter antihistamines online.
Treatment for anaphylaxis
If you or someone you know experiences a severe allergic reaction, you should seek emergency medical attention. Check to see if the person is breathing, call 911 or your local emergency services, and provide CPR if needed.
People with known allergies often have emergency medications with them, such as an epinephrine auto-injector (EpiPen, Adrenaclick, Auvi-Q). Epinephrine is deemed a rescue drug because it opens the airways and raises blood pressure.
The person may need your help to administer the medication. If the person is unconscious, follow these steps to help prevent shock:
- lay them on their side
- elevate their legs
- cover them with a blanket
Once you identify whats causing your allergic reaction, you can take the following steps:
- avoid exposure to the allergen
- seek medical care if youre exposed to the allergen
- carry medications to help treat anaphylaxis
You may not be able to avoid an allergic reaction completely, but these steps can help you prevent future allergic reactions.
If you have a known allergy, preventing an allergic reaction will improve your outlook. You can do this by avoiding your allergens whenever possible.
Your outlook will also depend on the severity of your allergy.
If you have a mild allergic reaction and seek treatment, youll have a good chance of recovery. However, symptoms may return if you come into contact with the allergen again.
If you have a severe allergic reaction, your outlook will depend on receiving quick emergency care, since anaphylaxis can result in death. If you have severe allergies, always carry an epinephrine auto-injector and inject yourself if symptoms occur.
Prompt medical care is also necessary to improve your outcome.
