An allergist is a doctor who specializes in diagnosing and treating allergic and immune system conditions. After completing medical school and a residency in internal medicine or pediatrics, these physicians complete an additional fellowship focused specifically on allergic and immunologic diseases. Their core expertise is identifying external triggers that cause disease and figuring out how to manage those reactions through testing, medication, and long-term immune-based therapies.
Allergies are remarkably common. About 25% of U.S. adults have seasonal allergies, nearly 7% have a food allergy, and close to 8% have eczema. Among children, roughly one in five has seasonal allergies and nearly 13% have eczema. With numbers that high, allergists fill a significant gap between what a primary care doctor can manage and what requires deeper investigation.
What Allergists Are Trained To Do
Becoming a board-certified allergist takes a minimum of nine years of training after college. That includes four years of medical school, three years of residency in internal medicine or pediatrics, and at least two years of fellowship in allergy and immunology accredited by the Accreditation Council for Graduate Medical Education (ACGME). Some fellowship programs run three years, with the additional time devoted to research. After completing training, allergists must pass a certification exam through the American Board of Allergy and Immunology and hold board certification in internal medicine, pediatrics, or both.
This training covers a wide range of conditions. Allergists treat hay fever, asthma, chronic cough, sinusitis, eczema, hives, food allergies, drug allergies, latex allergies, insect sting reactions, and anaphylaxis. They also manage immune deficiencies and occupational allergic diseases. One of their distinguishing skills is understanding how allergic conditions progress over time, a pattern sometimes called the “allergic march,” where a child with eczema may later develop food allergies, then asthma and hay fever.
Diagnostic Tests Allergists Use
A major part of an allergist’s job is pinpointing exactly what your immune system is reacting to. They use several types of testing, each suited to different kinds of allergic reactions.
The skin prick test is the most common. Small drops of liquid allergen extracts are placed on your forearm, and a sterile lancet presses each one into the top layer of skin. After 15 to 20 minutes, the allergist reads the results. A raised bump (called a wheal) 3 millimeters or larger indicates a positive reaction. This test works well for immediate allergic reactions like those triggered by pollen, pet dander, dust mites, and certain foods. It’s quick and gives results during the same visit.
For delayed reactions, like contact dermatitis from metals or chemicals, allergists use patch testing. Small chambers containing suspected allergens are taped to your back and left in place for 48 hours. The allergist reads the results after removing the patches, then checks again at 96 hours. Some allergens, particularly metals, may need a final reading at day seven.
Blood tests measuring allergen-specific antibodies (IgE) offer an alternative when skin testing isn’t practical, such as when you’re taking medications that could interfere with results or have a skin condition covering the testing area. For suspected food allergies, the gold standard is a double-blind, placebo-controlled food challenge, where you eat carefully prepared doses of the suspected food and a placebo under medical supervision while the allergist monitors for reactions.
Treatments Only an Allergist Provides
Beyond prescribing antihistamines and nasal sprays, allergists offer treatments that actually retrain the immune system. The most established of these is allergen immunotherapy, commonly known as allergy shots. Small, gradually increasing doses of the allergen are injected under the skin, typically every four to eight weeks during the maintenance phase, for a total of three to five years. Over time, this shifts the immune response away from the overreaction that causes symptoms and builds lasting tolerance. Multiple studies show sustained symptom relief that persists even after treatment ends.
Sublingual immunotherapy is a newer option that works on a similar principle but uses drops or dissolving tablets placed under the tongue daily instead of injections. It’s currently available for grass pollen, ragweed, and dust mite allergies. Oral immunotherapy for food allergies follows a related approach, with patients swallowing gradually escalating doses of the trigger food under close supervision.
Allergists also prescribe and manage biologic medications for severe asthma, chronic hives, and eczema that don’t respond to standard treatments. These are targeted therapies, usually given as injections every few weeks, that block specific parts of the immune pathway driving the allergic response.
Allergist vs. ENT vs. Dermatologist
There’s real overlap between allergists and other specialists, which can make choosing the right doctor confusing. An ENT (ear, nose, and throat doctor) treats many of the same sinus and nasal conditions, but their training includes surgical skills. If years of allergies have caused structural problems in your sinuses, like chronic blockages that don’t improve with medication, an ENT can perform procedures such as balloon sinuplasty. An allergist focuses on the underlying immune reaction driving those sinus symptoms in the first place.
Similarly, a dermatologist treats eczema and contact dermatitis from a skin-focused perspective, while an allergist approaches those same conditions by identifying the specific allergens or immune triggers involved and may offer immunotherapy as part of the treatment plan. For many patients with overlapping conditions, seeing both specialists at different stages makes sense.
When a Referral Makes Sense
Your primary care doctor can handle straightforward seasonal allergies in most cases. A referral to an allergist is typically warranted when symptoms persist despite standard treatment, when you’ve had a severe allergic reaction like anaphylaxis, or when you need help identifying what’s triggering your symptoms. Suspected drug allergies are another common reason for referral, especially if you’ve reacted to an antibiotic you may need again in the future or if you’re running out of medication options because of multiple suspected allergies. People with severe skin reactions to medications, recurrent infections suggesting an immune deficiency, or asthma that’s difficult to control also benefit from specialist evaluation.
What Your First Appointment Looks Like
An initial visit to an allergist typically lasts longer than a standard doctor’s appointment because it involves a detailed history and often same-day testing. A nurse will take your vitals, and then the allergist will spend time asking about your symptoms, when they occur, what makes them better or worse, your childhood allergy history, current medications, and your family’s history of allergic conditions.
If the office plans to run skin tests during that first visit, you may be asked to stop taking antihistamines for several days beforehand, since they can suppress the skin’s response and produce false negatives. Bring a list of all your current medications and any relevant medical records. Some offices may ask you to avoid eating for a certain period before the visit if food allergy testing is planned.
By the end of the appointment, you should leave with a clearer picture of what’s causing your symptoms, strategies for reducing your exposure to identified triggers, any necessary prescriptions, and a plan for follow-up testing or treatment if needed. For conditions requiring immunotherapy, that process typically begins at a subsequent visit after test results are fully evaluated.