Allergy diseases are referred to as the disorder of the immune system, often known as atopy. Allergic reactions occur to environmental substances known as allergens; these reactions are acquired, predictable and rapid. Strictly, allergy is one of four forms of hypersensitivity and is called type I (or immediate) hypersensitivity and it is characterised by excessive activation of certain white blood cells called mast cells and basophils by a type of antibody known as IgE, resulting in an extreme inflammatory response later known as allergy diseases. Common allergy diseases include eczema, hives, hay fever, asthma, food allergies, and reactions to the venom of stinging insects such as wasps and bees.

Allergic Rhinitis, one of the allergy diseases is defined as inflammation of the nasal membranes. It is characterised by a complex symptom that consists of any combination of sneezing, nasal congestion, nasal itching, and rhinorrhea. The eyes, ears, sinuses, and throat can also be involved in Allergic Rhinitis. Allergic rhinitis is the most common cause of rhinitis and is extremely common condition, affecting approximately 20% of the Indian population. While allergic rhinitis is not a life-threatening condition, several complications can occur and the condition can damage one`s health, which leads to a number of indirect costs.

Asthma is an allergy disease that affects the lungs and the airways that deliver air to the lungs. It causes periodic attacks of wheezing and difficult breathing. An asthma attack occurs when the airways become inflamed in response to a trigger, such as dust, mold, pets, exercise or cold weather. The latter may inflame the airways to the lungs, and the mucous membrane covering the walls becomes swollen with fluid allowing disease-fighting cells to accumulate and causing swelling in the lungs. Due to which, the airways become blocked or obstructed when the muscles surrounding the lungs tighten or go into spasm. Due to the blockage, air cannot flow in and out of the lungs freely and a whistling or wheezing sound may be heard. Such attacks can range from mild, moderate, or severe, and can last for a few minutes, a few hours, or several days.

Atopic dermatitis, a type of eczema and an inflammatory, chronically relapsing, non-contagious and pruritic skin disease is skin disease that has been given names like "prurigo Besnier," "neurodermitis," "endogenous eczema," "flexural eczema," "infantile eczema," and "prurigo diathsique". The skin of a patient with atopic dermatitis reacts abnormally and easily to irritants, food, and environmental allergens and becomes red, flaky and very itchy. It also becomes susceptible to surface infections caused by bacteria.

Urticaria or hives are a kind of allergic disease or skin rash notable for dark red, raised, itchy bumps. Hives are frequently caused by allergic reactions, however there are many non-allergic causes. For example, most cases of hives that lasts less than six weeks is the result of an allergic trigger. Chronic urticara are rarely due to an allergy. The majority of patients suffer from chronic hives from an unknown cause. Acute viral infection is another common cause of acute urticaria and causes of hives include friction, pressure, temperature extremes, exercise, and sunlight. It may be true that hives are more common in those with fair skin.

A variety of tests now exist to diagnose allergic diseases; these include testing the skin for responses to known allergens or analysing the blood for the presence and levels of allergen-specific IgE. Treatments for allergic diseases include allergen avoidance, use of anti-histamines, steroids or other oral medications, immunotherapy to desensitise the response to allergen, and targeted therapy of allergic diseases.