Allergy/Immunology is a specialty of medicine which deals with diagnosis and treatment of asthma, allergies. An allergy is an abnormal reaction to a substance or environmental trigger. Doctors specializing in this field are called Allergists. Allergists determine what substances or triggers cause reactions in each individual and look for ways to treat those allergies, so the sufferer can go on to live a normal life. Allergists may perform allergy tests like skin challenge, scratch test, breathing test to make accurate diagnosis and provide the right treatment plan.

Critical care is provided for patients who are suffering from life-threatening conditions. The doctors who work with these people are often called intensivists. They focus on a range of different issues, so they can serve people who need immediate and life-saving care. Since people who need critical care are suffering from such a wide variety of issues, intensivists must have a thorough understanding of diverse types of medical issues and the devices and medications needed to treat them.

An internist or Internal Medicine doctor is someone who specializes in diagnosing and treating illnesses, diseases, and health problems. Most internists are also primary care doctors and treat patients on a regular basis. They can diagnose and treat common illnesses or more serious problems. Most people see an internist regularly. Those with chronic illnesses may do so on a monthly or even weekly basis. Internists are the most common types of doctors.