Three categories of allergies

An allergic response occurs when your immune system reacts abnormally to a common substance in the environment. That substance is known as an allergen. It causes an inflammatory response in the body that may range from mild to life-threatening.

Allergies are a common problem, and it’s on the rise. The number of children with allergies has increased in the United States. It’s believed that the increase in allergies is a result of pollution, genetic components, and improved hygiene.

Allergic reactions may be caused by a number of different allergens. They’re generally broken down into three categories:

  • Ingested allergies are caused when an offending allergen is eaten.
  • Contact allergies occur when a substance such as a hair dye or detergent comes in contact with a person’s skin. This is also known as contact dermatitis.
  • Inhaled allergies are the most common type of allergy. They’re caused when a person breathes in an allergen such as pollen or animal dander.

Ingested allergies

A food allergy is a type of food intolerance in which a person’s immune system abnormally reacts to food. It’s also known as food hypersensitivity. It’s more common for children to have food allergies than adults. Food allergies are most often caused by:

  • cow’s milk
  • nuts
  • eggs
  • fruit

Symptoms of food allergies can be mild. Such is the case with hives. Hives can appear when certain foods are eaten. Most people with allergies have elevated levels of food-specific immunoglobulin IgE in their bloodstream. These are antibodies that bind to the allergen and then attach to mast cells in the skin. The mast cells in turn release histamine, which triggers a release of fluid that causes red, itchy, and inflamed skin — known as hives.

More severe symptoms of ingested allergies may include:

  • abdominal cramps
  • vomiting
  • diarrhea
  • skin rash
  • swelling of the lips and eyes which appears and disappears quickly
  • anaphylaxis, a sudden, extreme allergic reaction characterized by difficulty breathing, swelling of the tongue or throat, and may result in death

Any food allergy can progress to anaphylaxis, even if previous exposure reactions have been mild.

Children with food allergies may exhibit behavioral signs such as crying, irritability, or milk refusal.

Contact allergies

Contact allergies occur when an allergen touches a person’s skin.

The symptoms of this type of allergy are usually confined to the area of contact with the skin. Common irritants include:

  • soaps
  • detergents
  • hair dyes
  • jewelry
  • solvents
  • waxes
  • polishes

Natural allergens include ragweed.

Though annoying, a contact allergy is rarely dangerous. Symptoms of a contact allergy may include skin:

  • redness
  • itching
  • swelling
  • scaling
  • blistering

The best way to deal with a contact allergy is to identify and avoid the irritant. Treatments may include:

  • creams or ointments to help calm symptoms
  • antihistamines to prevent an allergic reaction
  • an anti-inflammatory medication such as prednisone in the most serious cases

With treatment, contact allergies usually resolve in a few days. But contact your doctor if there’s drainage from a rash accompanied by pain or fever, or if red streaks emanate from the rash. These are all signs of an infection rather than an allergic reaction.

Inhaled allergies

Inhaled allergies are the most common type of allergy. Symptoms may include:

  • sneezing
  • runny nose
  • watery eyes
  • itchy eyes

Many people who have inhaled allergies only experience symptoms during certain seasons. Pollen, grass, and mold are the most common triggers of seasonal allergies.

Pollen is a fine powder that comes from trees, weeds, and grass. Each season, beginning in the spring and continuing through the fall, the amount of pollen in the air increases. This increase may trigger allergic symptoms in people sensitive to pollen.

Avoiding pollen isn’t always as simple as retreating inside during allergy season. Other types of airborne allergens are prevalent indoors. These include:

  • fungi
  • mold
  • pet dander
  • dust mites

Many people confuse hay fever with asthma. Asthma is a chronic inflammatory disorder that causes bronchial swelling and constriction. It may be triggered by hay fever if a person has both conditions.

But hay fever and asthma are very different. A number of other factors can trigger an asthma attack, including:

  • a respiratory infection
  • certain drugs
  • other types of allergens, such as dust mites or diesel fumes
  • cold air
  • certain emotions and stress