An allergy is an immune system response to a substance that the body perceives as harmful, even though it may not be harmful to others. These substances are known as allergens and can trigger an allergic reaction when they come into contact with the body.

Types of allergies

1. Seasonal Allergies: Seasonal allergies, also known as allergic rhinitis or hay fever, are triggered by allergens that are only present during certain times of the year. Common seasonal allergens include pollen from trees, grasses, and weeds.

2. Perennial Allergies: Perennial allergies are triggered by allergens that are present year-round, such as dust mites, pet dander, and mold spores.

3. Food Allergies: Food allergies occur when the immune system reacts to a particular protein found in a certain food. Common food allergens include peanuts, tree nuts, shellfish, eggs, and milk.

4. Insect Allergies: Insect allergies occur when the immune system reacts to the venom or saliva of certain insects, such as bees, wasps, and mosquitoes.

5. Drug Allergies: Drug allergies occur when the immune system reacts to a particular medication. Common medications that can cause allergic reactions include antibiotics, aspirin, and non-steroidal anti-inflammatory drugs (NSAIDs).

6. Contact Allergies: Contact allergies occur when the skin comes into contact with an allergen, such as poison ivy or nickel.

7. Occupational Allergies: Occupational allergies are triggered by allergens in the workplace, such as chemicals or dust.

Symptoms of allergy

Allergic reactions can range from mild to severe and may include:

Itchy or runny nose


Watery or itchy eyes

Nausea or vomiting

Skin rash or hives

Shortness of breath

Wheezing or coughing


Allergies are diagnosed through a combination of medical history, physical examination, and allergy testing. Skin prick tests, blood tests, and patch tests are common tests used to diagnose allergies.


Common allergens include:


Dust mites

Animal dander

Mold spores

Nuts, milk, eggs, wheat, soy

Medications, such as penicillin

Insect bites and stings


Foods, such as peanuts, tree.

Risk factors

Certain factors may increase a person's risk of developing allergies, including:

Genetics: A family history of allergies increases the likelihood of developing allergies.

Age: Allergies can develop at any age, but they are more common in children.

Environmental factors: Exposure to pollution, cigarette smoke, or other environmental factors can increase the risk of developing allergies.

Previous allergic reactions: A person who has had an allergic reaction in the past is more likely to have future allergic reactions.


Treatment for allergies depends on the severity of the allergic reaction. Mild to moderate symptoms may be treated with antihistamines or nasal corticosteroids. Severe allergic reactions may require epinephrine (adrenaline) and immediate medical attention. Allergen immunotherapy (allergy shots) may be recommended for people with severe allergies or allergies that interfere with daily life.