An immunologist is a medical doctor who specializes in the study of the immune system, its functions, and its disorders. They are trained to diagnose, treat, and prevent diseases and disorders related to the immune system, such as allergies, autoimmune diseases, and immune deficiency disorders.

Some of the main tasks that an immunologist performs include:

• Diagnose and treat immune system disorders.
• Prescribing medication, such as immunosuppressants, to manage the symptoms of autoimmune disorders.
• Administering immunotherapy, such as allergy shots, to help desensitize patients to allergens.
• Advising patients on lifestyle changes and management strategies to help reduce symptoms.
• Coordinating care with other specialists such as rheumatologists, allergists, and hematologists.
• Conducting research to improve understanding of the immune system and develop new treatments for immune-related disorders.

An allergist is a medical doctor who specializes in the diagnosis and treatment of allergies and immune system disorders. They are trained to identify and manage a wide range of allergic and immune-mediated conditions, including:

• Allergic rhinitis (hay fever)
• Asthma
• Eczema (atopic dermatitis)
• Food allergies
• Drug allergies
• Insect sting allergies
• Anaphylaxis
• Chronic hives (urticaria)
• Immunodeficiency disorders

Some of the main tasks that an allergist performs include:

• Conducting skin tests and other diagnostic tests to identify the specific allergens that are causing symptoms
• Prescribing medication, such as antihistamines, to manage the symptoms of allergies
• Administering immunotherapy, such as allergy shots, to help desensitize patients to allergens
• Advising patients on lifestyle changes and management strategies to help reduce symptoms
• Coordinating care with other specialists such as pulmonologists, immunologists, and dermatologists
• Conducting research to improve understanding of allergies and develop new treatments

There are several different tests that allergists use to diagnose allergies, including:

1. Skin prick test: A small amount of allergen extract is placed on the skin, usually on the arm or back, and a small prick is made through the extract with a needle. This test is used to identify immediate allergic reactions to various allergens.
2. Intradermal test: Similar to the skin prick test, but the allergen extract is injected into the skin using a small needle. This test is used to identify allergies to specific allergens, such as venom from insect stings.
3. Blood test: A blood sample is taken and sent to a laboratory for analysis. These tests are used to measure the level of allergen-specific antibodies in the blood, which can indicate an allergic reaction. These are also called RAST (Radioallergosorbent test)
4. Patch test: A small patch containing an allergen extract is applied to the skin, usually on the back, and worn for 48 hours. This test is used to identify delayed allergic reactions to allergens that come into contact with the skin, such as poison ivy or nickel.
5. Challenge test: An allergist will give a small dose of allergen to the patient under close medical supervision, usually through the nose or mouth. This test is used to confirm a diagnosis of a food allergy or an allergy to a medication.

These tests help allergists to identify the specific allergens that are causing symptoms, and then make recommendations for treatment and management of the allergies.