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People are not born allergic to things, but they can be born with a genetic tendency to become allergic to things to which they are exposed, said John M. Kelso, MD, in a presentation at American College of Physicians (ACP-IM) Internal Medicine Meeting 2025.

Kelso, a professor of adult and pediatric allergy and immunology at the Scripps Clinic, San Diego, reviewed high-value approaches for managing patients with allergies triggered by food, medications, or environmental exposures.

Food Allergy Factors

When a patient says they have a food allergy, get them to tell a story about what they mean, said Kelso in his presentation. Find out the usual time interval between consumption of the food and development of symptoms, for example, he said.

Most children with milk or egg allergies outgrow them, and most adults with food allergies are allergic to tree nuts, such as almonds or pecans, peanuts, or fish/shellfish, he said. The vast majority of documented reactions, including most fatal reactions, have been to these common allergens, Kelso added.

Allergic reactions to foods can occur immediately or up to about an hour after eating, Kelso said. Symptoms of food allergies present in locations where mast cells release histamine, mainly the skin, respiratory tract, and gastrointestinal (GI) tract, Kelso said in his presentation.

Skin reactions to foods include flushing, swelling, itching, or hives. Respiratory reactions include red, watery, or itchy eyes; stuffy, runny, or itchy nose; and sneezing, Kelso said. Nausea, vomiting, diarrhea, and stomach or uterine cramps also may affect patients with food allergies. GI symptoms with food allergies almost never occur in isolation; there are almost always skin reactions as well, he said.

Food allergy reactions that could turn fatal include voice changes and difficulty swallowing or breathing, as well as asthma symptoms such as cough, wheeze, chest tightness, or shortness of breath, Kelso noted. Cardiovascular responses to an allergen including hypotension, angina, and dysrhythmias also can be fatal, Kelso said.

In cases of food allergy, prior uneventful ingestion of a food does not exclude a diagnosable allergy, but subsequent uneventful ingestion largely excludes it, said Kelso.

For a positive diagnosis, evidence of a specific immunoglobulin E (IgE) antibody is needed, he noted. 

However, do not order the “food panel” for food allergy testing; test only for suspected allergens and not for foods that the patient eats without reactions, Kelso noted. “There are no clinical circumstances where evaluating specific IgE [responses] to a panel of common food allergens is appropriate,” he said.

For the most value, test a specific suspect food in patients who show signs of an IgE-mediated food allergy, such as hives within an hour of consuming the food, said Kelso. These patients also may have concomitant respiratory or GI symptoms, or signs of hypotension.

IgE testing and removal of foods from the diet based on this testing is not appropriate in patients with such symptoms as chronic hives, chronic GI symptoms, or chronic systemic symptoms such as brain for or fatigue, Kelso emphasized.

As for ongoing management, subsequent reactions to a food are generally similar to past reactions, but they can occasionally be worse; therefore, “even patients who have had only hives as a reaction should have an epinephrine injector available,” Kelso said. Epinephrine injectors and the recently approved epinephrine nasal spray are available options, but patients experiencing reactions that do not respond to epinephrine should go to the emergency department because the reaction could progress, Kelso added.

Drug Allergy Dilemmas

In cases of an adverse event following medication, the medication may have been the cause of the adverse event, or it may have been coincidental, Kelso said in his presentation. “If the medication was the cause of the adverse event, it may or may not have been immunologically mediated vs a side effect of the medication,” he said.

However, if the reaction is immunologically mediated, that means there is a possibility of recurrence. “If this reaction is sufficiently bad, we will tell patients not to take that medication again in the future,” Kelso said in the presentation.

Late-Onset Reactions to Medications: Simple or Serious

Serious late-onset reactions to medications are hard to miss, Kelso said. They include Stevens-Johnson syndrome/toxic epidermal necrolysis, drug reaction with eosinophilia and systemic symptoms, and acute generalized exanthematous pustulosis.

Less severe late-onset reactions include a “drug rash,” which is a maculopapular rash, usually on the trunk, of a patient who otherwise feels well, Kelso said. A serum sickness–like reaction, more common in children, may involve dermatitis, fever, and arthralgia, he said. Erythema multiforme involves targeted lesions. “We used to think that was on the road to Stevens-Johnson syndrome, but we don’t think that anymore,” Kelso noted.

Late-onset reactions to medications are immune-mediated, but not IgE-mediated, so skin testing is not helpful, and no current test can prove causality or predict recurrence; “you have to work based strictly on the patient history,” Kelso said.

Severe reactions are an absolute contraindication to taking the medication, said Kelso. However, in many cases patients who experience drug rash or minor symptoms can finish a course of medication if it is important for treating another health condition, with attention paid to ensure that any reactions don’t evolve into something more serious, he said.

Penicillin Primer 

“The overwhelming majority of patients who are labeled as allergic to penicillin are not,” Kelso said. Given that the alternatives to penicillin are often less effective, more expensive, and come with side effects of their own (such as Clostridium difficile), there has been a movement toward “de-labeling” individuals who have been labeled as penicillin-allergic and ruling it out, said Kelso.

Patients who have penicillin allergy on their chart but have no history of severe cutaneous adverse reactions are candidates for de-labeling, Kelso said.

For patients who experienced hives after a first dose of a new course of penicillin, an intradermal skin test can confirm; blood tests are not reliable, he said. For patients whose histories do not include such immediate reactions or serious late-onset reactions, give them an amoxicillin challenge in the office and watch them for an hour, and those with no reaction can be de-labeled in their charts, he added.

Allergic Rhinitis Awareness

Patients with allergic rhinitis present with nasal symptoms including rhinorrhea, congestion, sneeze, or itch, said Kelso. To help confirm an allergy, ask patients about eye symptoms, seasonality, triggers, and family history, he said.

“Once we have identified a potential allergy to airborne allergens, you need to do a panel because you can’t see the pollen or animal dander,” he said.

The panel can help identify whether the patient has allergic rhinitis and pins down what specific item is causing the allergen, and whether it is under the patient’s control (such as cat dander).

“The bigger the skin test or higher value on the blood test, the more likely the allergy,” Kelso said. Antihistamines are the common treatment. Nasal corticosteroids can be used in addition for patients with more persistent symptoms, he noted.

For some patients, subcutaneous immunotherapy (allergy shots) is helpful, but only after 3-5 years of regular use, Kelso said. Many patients notice improvement after that time and can discontinue other allergy medications, However, remind patients that shots are not a substitute for environmental control, he said.

How Increased Allergy Prevalence May Play Out in Primary Care

Many allergic conditions are on the rise in the United States and patients may first present in primary care, said S. Shahzad Mustafa, MD, an allergy specialist and clinical associate professor of medicine at the School of Medicine and Dentistry, University of Rochester, Rochester, New York, in an interview.

A notable factor contributing to an increase in food allergies in children is the delay by parents and caregivers in the introduction of highly allergic foods to the infant diet, said Mustafa. “Earlier introduction of these foods likely decreases the chance of developing food allergy,” he said.

As for environmental allergies, successful management of allergic rhinitis involves a combination of environmental modifications, medical therapy, and immunotherapy, Mustafa told Medscape Medical News. “There is exciting research being done in different methods to administer immunotherapies, which have historically been administered with allergy ‘shots,’” he said. US Food and Drug Administration–approved sublingual tablets provide a welcome alternative and additional routes are being explored, including intra-lymphatic injections, Mustafa added.

Kelso had no financial conflicts to disclose. Mustafa disclosed serving on the speakers’ bureau for Genentech, GSK, AstraZeneca, CSL Behring, Regeneron/Sanofi, and ARS, and receiving grants from Takeda.