Allergy Symptoms: How to Recognize Them, What Tests Really Show, and What Athletes Should Know

Key Takeaways

The classic allergy symptoms of hay fever are nasal congestion, runny nose, postnasal drip, sneezing, and itching of the eyes, nose, and throat.[1]
In an expert consensus, itchy eyes and sneezing in bursts were rated as typical of allergic rhinitis rather than a cold,[2] and a 2020 expert statement described cough and fever as the most prominent COVID-19 symptoms.[3]
In my clinical experience, fever and a decline in overall condition point more toward infection than allergy, although both can occur at the same time.
Allergic rhinitis is associated with poorer sleep quality and more daytime sleepiness, with no significant difference in sleep duration.[4]
A positive allergy test is not the same as an allergy. Many healthy people test positive without any symptoms.[5]
In my practice, many antibiotic allergy labels, most often penicillin, go back to a childhood rash and have never been confirmed. In my view, relatively few of them are true allergies.
In my experience, parents may interpret symptoms such as stomach upset or a crying baby as allergy and start avoidance diets without the allergy being confirmed.
In my clinical experience, urticaria can have causes other than allergy, such as a viral infection, and the cause often remains unclear.
Sudden breathing difficulty, throat involvement, or a drop in blood pressure after exposure to a likely allergen may indicate anaphylaxis, for which intramuscular adrenaline is first-line treatment.[6]
In randomized trials, intranasal corticosteroids improved nasal and eye symptoms more than oral antihistamines.[7]

Introduction: Why Allergy Symptoms Are Easy to Misread

Allergic rhinitis alone is estimated to affect about 15% of the US population, roughly 50 million people, and it is linked with asthma, eczema, recurrent sinusitis, cough, and both tension-type and migraine headaches.[1] Yet allergy symptoms can be confused with colds or other infections,[2] and a positive allergy test does not by itself indicate allergic disease.[5]

Allergy symptoms can affect the nose, eyes, airways, and skin, and they vary widely from person to person. In my practice, the allergy I encounter most often is pollen allergy, which flares up in many patients every spring. I can see this directly in the number of prescription renewals for allergy medication that arrive at that time of year. Because the pollen season returns every year, symptoms in these patients often follow the same seasonal pattern.

This article covers what allergy symptoms actually look like in the nose, eyes, mouth, skin, and airways; how to separate them from infections; what allergy testing can and cannot tell you; which symptoms are an emergency; and what is specific to athletes.

What Causes Allergy Symptoms?

In allergic rhinitis, a weakened epithelial barrier in the nose lets allergens penetrate the lining, which triggers a T-helper type 2 inflammatory response and the production of allergen-specific IgE antibodies.[1]

In anaphylaxis, most allergens act through an IgE-mediated pathway, although some triggers can act independently of IgE, for example through direct activation of mast cells.[6]

Common Allergy Symptoms by Body Area

Nose and Sinuses

Allergic rhinitis typically presents with nasal congestion, rhinorrhea (runny nose), postnasal drainage, sneezing, and itching of the eyes, nose, and throat.[1] A JAMA review reports that in one international study, nasal congestion was present in 94.23% and rhinorrhea in 90.38% of patients with allergic rhinitis.[1]

In practice, the nasal picture varies. In some of my patients the nose runs constantly, sometimes for a long time, and may also be blocked, and many patients sneeze a great deal.

The timing of allergy symptoms matters. In the classification summarized in a 2024 JAMA review, allergic rhinitis is classed as intermittent when symptoms occur on fewer than 4 consecutive days a week or for fewer than 4 consecutive weeks a year, and persistent when they occur more often than 4 consecutive days a week and for more than 4 consecutive weeks a year.[1]

Not every runny nose is allergic. People with nonallergic rhinitis mainly have congestion and postnasal drainage, often with sinus pressure and ear symptoms, and their specific IgE tests to airborne allergens are negative.[1]

Eyes

Itching of the eyes is one of the core allergy symptoms in allergic rhinitis.[1] In an international expert consensus, eye itching and eye redness were rated as common in allergic rhinitis but not as features of the common cold.[2]

Allergic conjunctivitis can be difficult to tell apart from infectious conjunctivitis. In my clinical experience, allergic conjunctivitis often comes on somewhat faster and affects both eyes at the same time. Chemosis, a swelling of the conjunctiva, may also be more common in the allergic form. The eyes usually water heavily rather than producing a sticky discharge, and in my patients the symptoms may worsen when they go outdoors.

Airways and Asthma

Allergic rhinitis is associated with asthma.[1] In my practice, allergic asthmatics in particular are a group whose asthma tends to worsen during the allergy season. Many of these patients already use inhaled medication, often a corticosteroid combined with a long-acting bronchodilator. Some of my patients need inhaled medication only during the allergy season. I also see patients who have never been diagnosed with asthma but who develop asthma-like symptoms in connection with their allergies.

Mouth and Throat After Eating Certain Fruits

Some people with seasonal allergic rhinitis develop itching, stinging, or swelling in the mouth and throat after contact with certain foods. This is pollen food allergy syndrome. In a multicenter study of 815 patients with seasonal allergic rhinitis in seven Southern European countries, 167 (20.5%) reported such reactions; kiwi, peach, and melon were the most common triggers, most reactions were local, and 65.5% of reactions began within 5 minutes of contact with the food.[8] Prevalence varied widely between centers, from 7.5% in Marseille to 41.4% in Rome, and the authors suggest that differences in pollen sensitization patterns between regions may explain part of this variation.[8]

Skin

Hives, itching, flushing, and swelling (angioedema) are among the allergy symptoms that can affect the skin, for example during anaphylaxis.[9] Skin symptoms on their own are not classified as anaphylaxis, but together with significant symptoms from another organ system they are one of the criteria used to recognize it.[6]

Another group of patients may not have respiratory symptoms at all and instead develop urticaria (hives). From a clinical perspective, urticaria warrants some investigation, because it can have causes other than allergy. It may, for example, be triggered by a viral infection, or it may be idiopathic, in which case the cause often remains unclear. In practice, I try to work out whether there is a predisposing factor in the background: has the patient eaten something unusual, been exposed to a potential allergen, or recently had an illness?

Often no explanation is found, and the urticaria is then classified as idiopathic. These cases are usually treated symptomatically with antihistamines. If the urticaria does not settle, I refer the patient to an allergology specialist fairly readily.

Food Allergy: Perceived vs. Confirmed

In population estimates, self-reported food allergy is far more common than challenge-confirmed food allergy. An updated European systematic review of 110 studies found a pooled lifetime prevalence of self-reported food allergy of 19.9% and a point prevalence of 13.1%, while the point prevalence of a positive food challenge was only 0.8%.[10] The same review found a point prevalence of IgE sensitization of 16.6% by specific IgE and 5.7% by skin prick test.[10] These pooled estimates come from different studies and diagnostic methods, so they show that reported food allergy, IgE sensitization, and challenge-confirmed allergy are different measures rather than results in the same individuals.

In practice, many different symptoms end up being interpreted as allergy, especially stomach upset after a particular food or substance. In my experience, parents may interpret a wide range of symptoms in their children as allergic and start avoidance diets without an allergy having been confirmed together with a healthcare professional. This can be problematic and may lead to a vicious circle. For some parents, a baby simply crying a lot is enough to conclude that the baby is allergic to something, and abdominal pain in particular is easily interpreted as an allergic symptom. Before interpreting a child’s symptoms as allergy, it may be worthwhile to see a pediatrician.

Allergy Symptoms or a Cold? How to Tell the Difference

The overlap with viral infections is real, but a few features help. An ARIA-EAACI-GA²LEN expert consensus, built with a modified Delphi process from 87 analyzed questionnaires, rated sneezing as very common and occurring in bursts in allergic rhinitis, whereas it was rated common but not in bursts for the common cold.[2] Eye itching was rated common in allergic rhinitis and absent in the common cold.[2]

A 2020 EUFOREA expert statement, written early in the pandemic, summarized the distinction from COVID-19 along similar lines: cough and fever are the most prominent COVID-19 symptoms, while conjunctivitis and itching point toward allergic rhinitis.[3] The same statement noted that sudden, complete loss of smell may be an early sign of COVID-19 that separates it from allergic rhinitis.[3]

Some allergies closely resemble the symptoms of an infection, and patients are not always sure which one they are dealing with. A rule of thumb I use in practice is that if a patient develops a fever, a cold is the more likely explanation. A cold and an allergy can, of course, also occur at the same time. In my clinical experience, cold symptoms tend to evolve more over the course of the illness, often with cough and mucus. Cough and mucus can occur in allergy as well, but fever and a decline in overall condition remain typical signs of infection.

Allergy Symptoms That Affect Sleep and Daytime Function

Allergy symptoms rarely stop at the nose. A systematic review and meta-analysis of 27 observational studies, covering 240,706,026 people of whom 19,444,043 had allergic rhinitis, found no significant difference in sleep duration between people with and without allergic rhinitis.[4] However, people with allergic rhinitis had worse sleep quality, more sleep disturbance, longer sleep latency, and lower sleep efficiency.[4]

Allergic rhinitis was also associated with higher odds of insomnia, restless sleep, sleep-disordered breathing, obstructive sleep apnea, and snoring, and with daytime problems such as difficulty waking up, daytime sleepiness, and morning headache.[4] The authors rated the overall quality of evidence as low to very low, so these are associations, not proof that allergy causes each problem.[4]

Allergy Symptoms in Athletes

How Common Is Allergic Rhinitis in Athletes?

A systematic review of 13 studies found that the 10 studies reporting allergic rhinitis in athletes gave prevalence figures ranging from 21% to 56.5%.[11] Rhinitis overall seemed most common in swimmers (40%–74%), followed by cross-country skiers (46%) and track and field athletes (21%–49%).[11] The review did not find a convincing trend toward higher prevalence in land-based athletes than in the general population.[11]

Allergy and Exercise-Induced Bronchoconstriction

In athletes, atopy, defined in these studies as a positive skin prick test, is linked with exercise-induced bronchoconstriction. A systematic review of 60 studies including 7,501 athletes found an overall prevalence of exercise-induced bronchoconstriction (EIB) of 23%.[12] In the five studies that reported both EIB and atopy, atopy was present in 53% of athletes with EIB versus 41% of athletes without it, a statistically significant difference.[12]

Exercise-Induced and Food-Dependent Exercise-Induced Anaphylaxis

Exercise-induced anaphylaxis is defined as anaphylactic symptoms after physical activity, which may involve the skin (itching, flushing, hives, angioedema), airways (wheezing, shortness of breath), gut (nausea, vomiting, abdominal pain, diarrhea), and circulation (low blood pressure, collapse, loss of consciousness).[9] It is relatively rare.[9]

In about a third of cases a cofactor can be identified, such as food intake, warm or cold temperature, or drugs, especially non-steroidal anti-inflammatory drugs (NSAIDs).[9] The food-dependent form requires that neither the exercise nor the food alone causes a reaction, while the combination does.[9] When a cofactor is present before exertion, symptoms mostly develop within 30 minutes of starting activity.[9] The World Allergy Organization guidance also lists physical activity, sleep deprivation, and medication among cofactors of anaphylaxis.[6]

Antihistamines and Endurance Performance

In a study of 11 competitive cyclists, combined histamine H1 and H2 receptor blockade had no discernible effect on hemodynamic or metabolic variables, but it increased the time to complete a 10-km time trial by 10.5 ± 3.7 seconds compared with placebo.[13] This study used combined H1 and H2 blockade, not a standard single antihistamine for hay fever, so it does not show that a usual allergy tablet slows athletes down. The authors concluded that exercise-related histamine signaling appears to be inherent to endurance exercise and may play a role in optimal function during high-intensity endurance exercise.[13]

When Allergy Symptoms Are an Emergency

Anaphylaxis is defined by the World Allergy Organization as a serious systemic hypersensitivity reaction that is usually rapid in onset and may cause death.[6] Under the 2020 criteria, anaphylaxis is highly likely when either of the following occurs:[6]

Sudden onset, over minutes to several hours, of skin or mucosal symptoms such as generalized hives, itching or flushing, or swollen lips, tongue, or uvula, together with at least one of the following: respiratory compromise (such as shortness of breath, wheeze, or stridor), reduced blood pressure or related symptoms such as collapse or fainting, or severe gastrointestinal symptoms such as severe cramping abdominal pain or repeated vomiting, especially after exposure to non-food allergens.
Sudden low blood pressure, bronchospasm, or laryngeal involvement after exposure to a known or highly probable allergen, even without typical skin symptoms.

The guidance stresses that skin signs are absent in 10%–20% of anaphylactic reactions, which can delay recognition.[6] According to the guidance, intramuscular adrenaline (epinephrine) remains first-line treatment, and after an episode patients should be referred to a specialist to identify the cause.[6] For exercise-induced anaphylaxis, a review states that patients should carry an adrenaline autoinjector.[9]

In my view, anaphylaxis is the most feared allergy symptom, and it is also the situation patients fear most. In my emergency work, patients with anaphylaxis arrive from time to time. The onset is usually sudden, and it may be accompanied by urticaria, but not always. For these patients, the first priority is an adrenaline injection, after which they usually also receive a corticosteroid and an antihistamine. According to the WAO guidance, glucocorticoids and antihistamines are second-line medications: antihistamines have a limited role but can help relieve skin symptoms, and there is increasing evidence that glucocorticoids may be of no benefit in the acute management of anaphylaxis, so their routine use is becoming controversial.[6] Neither replaces adrenaline as first-line treatment.[9]

In the emergency department where I work, patients who arrive with urticaria are often given an antihistamine and a corticosteroid straight away, and we are ready to give adrenaline if anaphylaxis develops or there are signs pointing to it. Fortunately, this is rarely necessary. A rash on its own is usually less harmful, although unpleasant, and it worries clinicians much less than potential anaphylaxis.

Sudden breathing difficulty, throat or voice involvement, collapse, or a drop in blood pressure after exposure to a known or highly probable allergen may indicate anaphylaxis and needs emergency care.[6]

What Allergy Tests Can and Cannot Tell You

Skin prick tests and specific IgE blood tests detect sensitization, meaning IgE antibodies to an allergen. They do not by themselves prove that the allergen causes allergy symptoms.[5] In a study of 100 healthy volunteers with no known allergic symptoms, 42 had a positive skin prick test to at least one of 16 common airborne allergens, and the authors concluded that skin test reactivity without allergic symptoms does not indicate allergic disease.[5]

In the European food allergy estimates, the pooled point prevalence of IgE sensitization by blood test (16.6%) was also far higher than that of challenge-confirmed food allergy (0.8%).[10]

Many of my patients ask for allergy tests. Skin prick tests have traditionally been used, but in my practice IgE blood tests are now used more often. The clinical limitation of IgE testing is that a positive result alone does not necessarily mean allergy; it has to be interpreted against the patient’s clinical picture. In selected cases, greater certainty can come from a challenge test, which needs to be carried out under medical supervision.

Antibiotic Allergy Labels That Are Never Confirmed

In my daily work, I come across antibiotic allergies quite often, and in my experience most of them are penicillin allergies. Many of these labels go back to childhood: an ear infection, for example, was treated with amoxicillin or another antibiotic, and the child developed urticaria or another rash during the illness. In my view, relatively few of these are true antibiotic allergies, but few clinicians are willing to test that assumption. The label therefore tends to stay in the patient’s records as an allergy without ever being confirmed.

From a clinical perspective, this is difficult to resolve, because an IgE test alone does not rule out the allergy; a supervised challenge test may be needed, and in practice it is often hard to arrange. This is unfortunate, because if the patient is not truly allergic, the label can make it harder to find a suitable antibiotic, and if resistance later becomes a problem with another antibiotic, fewer options remain. Similarly, when a patient develops stomach upset or nausea from an antibiotic without other objective signs of allergy, I would be cautious about labelling it as an allergy straight away, while still taking appropriate care with that antibiotic in the future.

A CMAJ practice review states that about 10% of people report a penicillin allergy, but 90%–95% of those individuals are not truly allergic. The same review notes that the label is associated with the use of costly and less effective second-line and broad-spectrum antibiotics.[14]

Treating Allergy Symptoms: What the Evidence Supports

A JAMA review advises patients with allergic rhinitis to avoid the allergens that trigger their symptoms.[1] For medication, the same review lists a second-generation H1 antihistamine (for example cetirizine, fexofenadine, desloratadine, or loratadine) or an intranasal antihistamine for mild intermittent or mild persistent allergic rhinitis, and an intranasal corticosteroid, alone or with an intranasal antihistamine, as initial treatment for persistent moderate-to-severe allergic rhinitis.[1]

A 2024 systematic review and meta-analysis of 35 randomized trials in patients aged 12 years and older found that intranasal treatments outperformed oral treatments on the assessed symptom and quality-of-life outcomes, while in the pooled comparison, adverse events and withdrawals due to adverse events did not differ between intranasal and oral treatments; adverse events were, however, more frequent with intranasal than with oral antihistamines.[7] Intranasal corticosteroids improved nasal symptom scores, eye symptom scores, and rhinitis quality of life more than oral antihistamines; the certainty of evidence was low for nasal symptoms and high for eye symptoms and quality of life.[7] Most included trials studied seasonal allergic rhinitis.[7]

Conclusion: Allergy Symptoms Deserve Precise Attention

Allergy symptoms are common, and the classic picture of congestion, runny nose, sneezing, and itchy eyes, nose, and throat is well defined.[1] In an expert consensus, eye itching and sneezing in bursts were rated as favoring allergic rhinitis over a cold.[2] In my clinical experience, fever and a decline in overall condition point more toward an infection, although an allergy and a cold can also occur at the same time. Allergic rhinitis is associated with poorer sleep quality and daytime sleepiness.[4]

Allergy tests detect sensitization, not necessarily disease.[5] In my daily work, this is especially visible with antibiotic allergy labels: many go back to a childhood rash, and in my view relatively few are true allergies, yet they often stay in the patient’s records without ever being confirmed. In the same way, symptoms such as stomach upset or a baby crying a lot are easily interpreted as allergy without confirmation, and urticaria can also have causes other than allergy, with no cause found in many cases.

For athletes, allergy can overlap with exercise-induced bronchoconstriction and, rarely, exercise-induced anaphylaxis.[9][12] The most important distinction is recognizing anaphylaxis, a medical emergency in which intramuscular adrenaline is first-line treatment.[6]

Allergy Symptoms: How to Recognize Them, What Tests Really Show, and What Athletes Should Know

Table of Contents

Key Takeaways

Introduction: Why Allergy Symptoms Are Easy to Misread

What Causes Allergy Symptoms?