Omicron, Hay Fever, or a Cold: What’s the Diagnosis?

When the flu season started last year and the delta variant of the coronavirus was still around, it could be hard to tell the difference between COVID-19 and the flu. Both could make you feel seriously ill, with symptoms like fever, cough, shortness of breath, muscle aches, and severe fatigue. For a few people, the flu could be deadly, and the delta variant was deadly for many more.

As we head into spring and summer, the delta variant has been replaced by the omicron variant, and the flu has become much less common than seasonal allergies. For most people, omicron is more like allergies or a cold than delta was, although omicron can still be dangerous for unvaccinated people.

So how do you tell the difference? What tests should you use to make the right diagnosis?

Similar Symptoms

Early data shows that cold-like symptoms are the most commonly reported symptoms for people with omicron:1

• Runny nose.
• Headache.
• Fatigue, ranging from mild to severe.
• Sneezing.
• Sore throat.

The ailment is more likely to be a cold if your patient has additional symptoms such as fever, cough, aches and pains, and congestion.2

Allergy Symptoms

Omicron and colds are both caused by viruses that can be easily spread from person to person—usually by droplets coughed or sneezed into the air. Seasonal allergies, or “hay fever,” have a completely different cause. They are an immune system reaction in which normally harmless pollens in the air trigger an attack by the immune system, which treats the pollens as foreign invaders, attacking them much like it would a virus.3

The most common symptoms of hay fever are:3
• Itching of the nose, eyes, throat, and mouth.
• Sneezing.
• Stuffy nose.
• Runny nose.
• Tearing.
• Dark circles under the eyes.

Symptoms that are not caused by hay fever are severe fatigue, aches and pains, and fever. Sore throat is rarely caused by allergies. On the other hand, colds and omicron do not cause itching, tearing, or dark circles under the eyes.2

You should also suspect seasonal allergies if your patient has had similar allergy symptoms in the past at the same time of year. When spring allergies start depends on where you live. In general, if you live in an area where trees and grass grow in the spring, spring allergies usually start when trees start to bloom. They continue into the summer as the grass starts to grow and pollinate. Later in the summer and fall, weed pollens become common.4

Treatment Options

Cold. Patients probably won’t need any treatment for a cold other than over-the-counter cold medicines. COVID-19: In the absence of risk factors, no treatment is necessary. But if a patient has a weak immune system, is unvaccinated and over age 65, or is vaccinated and over age 75, consider an intravenous dose of monoclonal antibody.

Seasonal Allergies. The best treatment for hay fever is avoiding pollen during the allergy season. Advise patients to limit outdoor activities when the pollen count is high. (Check the National Allergy Bureau for allergy counts in your area.) Short-term treatments include antihistamine pills, antihistamine nasal
spray, steroid nasal spray, and nasal decongestant pills. Long-term treatment of hay fever is called immunotherapy. This therapy exposes the immune system to small amounts of allergens and slowly builds up the exposure over time until the patient’s immune system learns to control the allergy. Traditionally, immunotherapy consists of just allergy shots. A newer option is sublingual immunotherapy, which is instead a regimen of allergy tablets placed
under the tongue.4,6


When a patient presents with these symptoms, ask when they started and how long they’ve lasted. Ask about any history of allergies and if the patient has been in contact with anyone who’s had similar symptoms.4

If the symptoms and a physical exam do not lead to a diagnosis, diagnostic tests may be performed. Omicron can be diagnosed with two COVID tests. Both can be performed with a nose or throat swab:1,5

  • Nucleic acid amplification tests— most commonly, PCR tests—are the most accurate, but they must be sent to a lab, and receiving the results may take a day or two.
  • Antigen tests are point-of-care tests that yield results in about 15 minutes. These tests occasionally fail to detect infections, producing a false negative.

Diagnosing allergies has two purposes. A diagnosis can confirm that symptoms are due to allergies and also tell you what the patient’s allergies are, which can help the patient avoid them or help an allergist treat them. For allergy diagnosis, there are two testing methods:4,6

  • Skin testing uses a prick, scratch, or injection under the skin to expose the patient to a tiny amount of an allergen. If the skin reacts with redness or swelling, it confirms the allergy.
  • RAST or IgE testing. A blood sample is sent to a lab yo measure the allergic response to different allergens.

Consider that a patient may have more than one condition.


  1. Iacobucci G. Covid-19: runny nose, headache, and fatigue are the commonest symptoms of omicron, early data show. BMJ. 2021;375:n3103. doi:10.1136/bmj.n3103
  2. Mayo Clinic Staff. COVID-19, cold, allergies, and the flu: what are the differences? Mayo Clinic. Published March 3, 2022. Accessed March 30, 2022.
  3. American Academy of Allergy, Asthma & Immunology. Hay fever / rhinitis. Accessed March 30, 2022. add8af6c11ecb5b6c40617ee805a
  4. Bartolome S. Which COVID test is best? Pros and cons of coronavirus detection methods. UT Southwestern Medical Center. Published September 3, 2020. Accessed March 30, 2022.
  5. Cleveland Clinic. Allergy testing. Updated July 2, 2021. Accessed March 30, 2022.
  6. National Institutes of Health. Therapeutic management of nonhospitalized adults with COVID-19. NIH | COVID-19 Treatment Guidelines. Updated February 1, 2022. Accessed March 30, 2022.