The fastest way to tell allergies from COVID is to check for two things: fever and itchiness. Allergies almost never cause a fever, while COVID frequently does. And itchy eyes, nose, or throat are hallmarks of allergies that rarely show up with a viral infection. Beyond those two markers, the overlap between symptoms can be surprisingly large, especially with newer COVID variants that tend to cause milder, more cold-like illness. Here’s how to sort through it.
Symptoms That Point Toward Allergies
Seasonal allergies are an immune overreaction to things like pollen, dust, or mold, not an infection. That distinction drives the symptom pattern. The classic signs are itchy eyes, an itchy or tingling nose and throat, sneezing in clusters, a clear and watery runny nose, and congestion. You might also notice that your symptoms follow a predictable rhythm: worse in the morning, worse outdoors, worse on high-pollen days, and better when you come inside or turn on air conditioning.
Allergies don’t cause fever, body aches, or significant fatigue. If you feel physically wiped out or achy, that points away from allergies and toward a virus. Allergies also don’t cause shortness of breath on their own (unless you have asthma triggered by allergens), and they don’t produce a deep or persistent cough.
Symptoms That Point Toward COVID
COVID symptoms typically appear 2 to 14 days after exposure. The current variants tend to present with sore throat, cough, congestion, fatigue, headache, and sometimes fever or chills. Body aches and muscle pain are common. Some people experience gastrointestinal symptoms like nausea or diarrhea, which allergies essentially never cause.
Loss of smell and taste was once a signature COVID symptom, but it’s far less common now. With Omicron-era variants, the global prevalence of smell loss dropped to roughly 3.7%, compared to rates that were two to ten times higher with earlier variants like Alpha and Delta. In people of European ancestry, the rate is closer to 12%, but for most of the global population it sits below 5%. So while losing your sense of smell still suggests COVID over allergies, most people with current COVID infections won’t experience it.
Where the Symptoms Overlap
The tricky middle ground includes congestion, runny nose, sneezing, and mild cough. Newer COVID variants cause all of these, which makes them easy to confuse with allergies, especially during spring and fall when pollen counts are high. A few questions can help you narrow it down:
- Did symptoms come on suddenly after being outdoors? That pattern favors allergies. COVID symptoms build gradually over a day or two.
- Do you have a sore throat, body aches, or fatigue? These point toward COVID (or another virus). Allergies cause throat irritation from postnasal drip, but not the raw, painful sore throat typical of an infection.
- Are your eyes itchy and watery? Strong allergy signal. COVID can cause watery eyes occasionally, but the itch is distinctive to an allergic response.
- Do symptoms change with your environment? If going indoors, showering, or closing windows brings relief within an hour, allergies are the likely cause. Viral symptoms don’t respond to environmental changes.
The Antihistamine Test
One of the most practical clues is how your body responds to allergy medication. Allergies generally respond well to antihistamines or nasal steroid sprays, while COVID and other respiratory viruses do not, or only partially respond. If you take an antihistamine and your sneezing, runny nose, and itchy eyes clear up within 30 to 60 minutes, allergies are the most likely explanation. If the medication barely makes a dent, a virus becomes more probable.
This isn’t a perfect test. Antihistamines can partially dry up a runny nose regardless of the cause, and some people have both allergies and a virus at the same time. But a strong, clear response to allergy medication is reassuring.
When and How to Test for COVID
If you have any doubt, a rapid antigen test is the simplest next step. These produce results in 15 to 30 minutes and are widely available over the counter. The important caveat: a single negative rapid test doesn’t rule out COVID. The FDA recommends two negative antigen tests taken 48 hours apart if you have symptoms. If you don’t have symptoms but had a known exposure, three tests spaced 48 hours apart are recommended.
Rapid antigen tests are less sensitive than PCR (also called NAAT) tests, which are considered the gold standard and are processed in a lab. PCR results can take up to three days. If your rapid test is negative but your symptoms don’t match allergies and you want more certainty, a PCR test from a healthcare provider can confirm the result.
One wrinkle to keep in mind: if you tested positive for COVID within the last 90 days, a PCR test may still pick up remnants of the previous infection. In that situation, antigen tests are more reliable for detecting a new infection.
When Both Are Happening at Once
It’s entirely possible to have seasonal allergies and catch COVID simultaneously. If your usual allergy symptoms suddenly shift, pay attention. New fatigue, fever, sore throat, or body aches layered on top of your normal seasonal pattern are worth testing for. Allergies also inflame your nasal passages, which some researchers believe may make it easier for respiratory viruses to take hold, so allergy season and viral illness aren’t mutually exclusive.
If you’re a longtime allergy sufferer, you probably know your personal pattern well. Trust that knowledge. When something feels different from your usual spring or fall symptoms, that’s a meaningful signal to grab a test kit.