What is an allergic reaction?

Your immune system creates antibodies to fight off foreign substances so you don’t get sick. Sometimes your system will identify a substance as harmful even though it isn’t. When this happens, it’s called an allergic reaction.

These substances, or allergens, can be anything from food, medication, or environments.

When your body comes in contact with these allergens, it can cause mild symptoms like skin irritation, watery eyes, or sneezing. In some people allergies can cause anaphylaxis. Anaphylaxis is a life-threatening condition that will cause shock, a sudden drop in blood pressure, and trouble with breathing. This can lead to respiratory failure and cardiac arrest.

Call 911 immediately if you or someone you know is experiencing anaphylaxis.

What are the symptoms of an allergic reaction?

Your body’s allergic reaction depends on what you’re allergic to. Parts of your body that will react include your:

Common symptoms

Take a look at the table below to see which symptoms commonly show up for which allergy.

Environmental allergyFood allergyInsect sting allergyDrug allergy
Runny or stuffy nose
Skin irritation (itchy, red, peeling)
Trouble breathing
Nausea or vomiting
Short of breath, or wheezing
Watery and bloodshot eyes
Swelling around the face or contact area
Rapid pulse

Anaphylaxis or severe reactions

The most serious allergic reactions can cause anaphylaxis. This reaction occurs minutes after exposure and, if left untreated, can lead to loss of consciousness, respiratory distress, and cardiac arrest.

Signs include:

Get emergency help if you or someone you know is experiencing anaphylaxis, even if symptoms start to improve. Sometimes symptoms can return.

What to do when someone is experiencing anaphylaxis

If you’re with someone who is experiencing anaphylaxis, you should:

  • Call 911 immediately.
  • See if they have an epinephrine (adrenaline) auto injector and help them, if needed.
  • Try to keep the person calm.
  • Help the person lie on their back.
  • Raise their feet about 12 inches and cover them with a blanket.
  • Turn them on their side if they are vomiting or bleeding.
  • Make sure their clothing is loose so they can breathe.

The sooner the person gets their epinephrine, the better. Avoid giving oral medications, anything to drink, or lifting their head, especially if they’re having trouble breathing.

After the first anaphylaxis experience, your doctor can prescribe emergency epinephrine. The auto injector comes with a single dose of medication to inject into your thigh. You’ll want to teach your family and close friends how to inject the adrenaline in cause of an emergency.

CPR for anaphylaxis

If the person you’re with isn’t breathing, coughing, or moving, you may need to perform CPR. This can be done even without formal CPR training. CPR involves doing chest presses, about 100 per minute, until help arrives.

If you’re interested in learning CPR, contact the American Heart Association, American Red Cross, or a local first-aid organization for training.

Learn how to perform hands-only and mouth-to-mouth CPR here »

General treatments for allergic reactions

Over-the-counter (OTC) antihistamines and decongestants may relieve minor symptoms. Antihistamines prevent symptoms such as hives by blocking histamines receptors so your body doesn’t react to the allergens. Decongestants help clear your nose, especially for seasonal allergies. But don’t take them for more than three days.

These medications are available in tablets, eye drops, and nasal sprays. Many OTC drugs also cause drowsiness, so avoid taking them before driving or doing work that requires a lot of concentration.

Swelling, redness, and itching may be reduced with ice and topical creams that contain corticosteroids.

Make an appointment with your doctor if OTC drugs don’t work. Call the doctor right away if you have allergic reactions to the medication.

Pricing for allergy medication

Treatments for food allergies

The best remedies for food allergies usually entail avoiding foods that trigger an allergic reaction. If you accidentally come in contact or eat the food you’re allergic too, OTC drugs can temper the reaction. However, these drugs only help relieve hives or itching. Oral cromolyn, which is only available by prescription, can help your other symptoms.

You may also treat severe food allergies with epinephrine.

Pricing for food allergy medication

Treatments for plant or bite allergies

Poisonous plants

According to The Children's Hospital of Philadelphia, about seven out of 10 people have an allergic reaction when they touch poison ivy, poison oak, and poison sumac. The sticky substances from these plants, also called urushiol, bind to the skin upon contact.

Symptoms range from mild redness and itching to severe blisters and swelling. Rashes appear anywhere from three hours to a few days after contact and last one to three weeks.

If exposed to poisonous plants, you should:

  • Avoid touching other areas of your body, especially your face.
  • Clean the area with soap and water for at least 10 minutes.
  • Take a cool bath.
  • Apply calamine, or anti-itching, lotion three to four times a day to relieve itching.
  • Soothe inflamed areas with oatmeal products or one percent hydrocortisone cream.
  • Wash all clothing and shoes in hot water daily.

These steps all focus on removing the urushiol from your skin. Severe reactions in children may require a doctor’s visit to prescribe oral steroids or stronger creams to ease the symptoms.

You should see a doctor if you have a high temperature and:

  • the scratching gets worse
  • the rash spreads to sensitive areas like the eyes or mouth
  • the rash doesn’t improve
  • the rash is tender or has pus and yellow scabs

Despite claims, there’s no scientific evidence to support that scratching an open wound leads to poison in the bloodstream. The left over oil would only touch the immediate area. Avoid spreading the oil immediately by washing the affected area with soap and water.

Stinging insects

Most people will have a reaction to an insect bite, but the most serious reaction is an allergic one. About 2 million people in the United States are allergic to insect stings, according to the Cleveland Clinic.

Most common insect stings are from:

  • bees
  • wasps
  • yellow jackets
  • hornets
  • fire ants

Treat insect allergies by:

  • removing the stinger with a straight edge object, such as a credit card, and using a brushing motion (pulling or squeezing a stinger may release more venom into your body)
  • washing the area with soap and water and applying an antiseptic after
  • applying hydrocortisone cream or calamine lotion and covering the area with a bandage
  • applying a cold compress to the area, if there’s swelling
  • taking antihistamine to reduce itching, swelling, and hives
  • taking aspirin to relieve pain

Children and pregnant women shouldn’t take OTC medication as there may be unintended side effects like Reye’s syndrome, which is a rare but serious liver and brain disorder.

Jellyfish stings

If a jellyfish stings you, wash the area with seawater or vinegar for 30 minutes. This will neutralize the jellyfish’s toxin. Apply something cold on the affected area to soothe your skin and lessen pain. Use hydrocortisone cream and antihistamine to reduce swelling.

The British Red Cross advises that urinating on a jellyfish sting won’t help. In fact, it may actually increase pain.

Treatment for drug allergies

In most drug allergy cases, your doctor should be able to prescribe an alternative medication. Antihistamines, corticosteroids, or epinephrine may be needed for more serious reactions.

Otherwise, your doctor may recommend a desensitization procedure. This means taking small doses of the medication until your body can handle your dosage.

How to prevent allergic reactions

Once you’ve had an allergic reaction, it’s important to identify the source to avoid future contact. For ingredient-specific allergies, check product ingredients before purchase. Applying lotion before going hiking or camping may help to prevent poison ivy from spreading or absorbing into your skin.

The more control you keep over your contact with allergens, the less likely you’ll have an allergic reaction. Make sure your coworkers and friends know about your allergies and where you keep your epinephrine auto injector. Teaching your friends how to treat an allergic reaction can help save a life.