An allergic response to peanuts usually occurs within minutes after exposure. Peanut allergy signs and symptoms can include:

• Runny nose

• Skin reactions, such as hives, redness or swelling

• Itching or tingling in or around the mouth and throat

• Digestive problems, such as diarrhea, stomach cramps, nausea or vomiting

• Tightening of the throat

• Shortness of breath or wheezing

Anaphylaxis: A life-threatening reaction

Peanut allergy is the most common cause of food-induced anaphylaxis, a medical emergency that requires treatment with an epinephrine (adrenaline) injector (EpiPen, Symjepi, others) and a trip to the emergency room.

Anaphylaxis signs and symptoms can include:

• Constriction of airways

• Swelling of the throat that makes it difficult to breathe

• A severe drop in blood pressure (shock)

• Rapid pulse

• Dizziness, lightheadedness or loss of consciousness

Peanut allergy occurs when your immune system mistakenly identifies peanut proteins as something harmful. Direct or indirect contact with peanuts causes your immune system to release symptom-causing chemicals into your bloodstream.

Exposure to peanuts can occur in various ways:

• Direct contact. The most common cause of peanut allergy is eating peanuts or peanut-containing foods. Sometimes direct skin contact with peanuts can trigger an allergic reaction.

• Cross-contact. This is the unintended introduction of peanuts into a product. It's generally the result of a food being exposed to peanuts during processing or handling.

• Inhalation. An allergic reaction may occur if you inhale dust or aerosols containing peanuts, from a source such as peanut flour or peanut oil cooking spray.

It isn't clear why some people develop allergies while others don't. However, people with certain risk factors have a greater chance of developing peanut allergy.

Peanut allergy risk factors include:

• Age. Food allergies are most common in children, especially toddlers and infants. As you grow older, your digestive system matures, and your body is less likely to react to food that triggers allergies.

• Past allergy to peanuts. Some children with peanut allergy outgrow it. However, even if you seem to have outgrown peanut allergy, it may recur.

• Other allergies. If you're already allergic to one food, you may be at increased risk of becoming allergic to another. Likewise, having another type of allergy, such as hay fever, increases your risk of having a food allergy.

• Family members with allergies. You're at increased risk of peanut allergy if other allergies, especially other types of food allergies, are common in your family.

• Atopic dermatitis. Some people with the skin condition atopic dermatitis (eczema) also have a food allergy.

While some people think food allergies are linked to childhood hyperactivity and to arthritis, there's no evidence to support this.

Complications of peanut allergy can include anaphylaxis. Children and adults who have a severe peanut allergy are especially at risk of having this life-threatening reaction.