A rheumatologist is a physician who has received extensive training in diagnosing and treating rheumatic conditions. Rheumatic conditions involve the joints, soft tissues, autoimmune system, vascular system, and connective tissues.
Some of the conditions that rheumatologists treat are rheumatoid arthritis, ankylosing spondylitis, gout, sarcoidosis, vasculitis, and lupus. These are all conditions that involve a lot of pain and make mobility difficult. Rheumatologists use medications, such as analgesics, NSAIDs, steroids, DMARDs, infliximab, and adalimumab, as well as occupational therapy, in order to decrease pain and improve a patient's quality of life.

An allergy & immunology specialist is a physician who is specially trained in matters pertaining to chronic and acute allergies, as well as deficiencies of the immune system. The doctor will determine whether an allergy, which attacks our immune system, is present. They'll also determine the cause, whether it be environmental triggers like trees and pollen, food-borne like peanuts and dairy, the venom of insects like bees, or a medication like penicillin.
In addition to determining the allergen causing an immunological response in a patient, the specialist will treat the symptoms caused by the reaction.

An internist is a physician who focuses on the diagnosis and treatment of conditions that affect the adult population—both acute and chronic.
These doctors are often who adults see as their primary physicians because they treat a broad range of illnesses that do not require surgical or specialist interventions. They also work to help a patient maintain optimal health in order to prevent the onset of disease.
In addition to treating the common cold and flu, internists also treat chronic diseases like diabetes and heart disease.