Flu or Allergy? Differences Between Symptoms

Although complaints such as runny nose, sneezing, weakness and cough that occur during the seasons are considered by many people as a “simple cold”, various health problems such as flu or allergies can be underlying these symptoms.

Uzm. Dr.
Bilal Uğurlukişi
Internal Medicine (Internal Medicine)

Publication Date:

15/5/2026 4:32 PM

Allergy with flu is often confused, especially since the first symptoms are similar to each other. But the reason for the appearance of these two conditions, their course and methods of treatment are completely different from each other. The correct interpretation of the symptoms is of great importance so that the correct treatment can be started in a timely manner and the risk of complications can be avoided.

What is the Flu?

Influenza is an infectious respiratory infection caused by influenza viruses. It is more common, especially in autumn and winter, and can spread quickly indoors. Flu isn't just a simple upper respiratory infection; it can lead to pneumonia, bronchitis, and serious breathing problems in some people.

Flu symptoms usually start suddenly. A person may feel quite sluggish and exhausted in a few hours while healthy in the morning. Especially high fever and widespread body aches are among the most obvious features of the flu.

What Are the Symptoms of Flu?

The most common symptoms of influenza are:

• High fever of 38 degrees and above

• Feeling of chills and chills

• Severe muscle and joint pain

• Intense weakness and loss of energy

• Dry cough

• Sore throat

• Headache

• Nasal congestion or runny nose

• Loss of appetite

Flu symptoms usually begin to ease within 5 to 10 days. However, the feeling of coughing and fatigue can persist for weeks in some people.

What is Allergy?

Allergy is a condition in which the immune system overreacts to substances that are normally harmless, such as pollen, house dust mites, animal hair, mold, or certain chemicals. Allergy is not contagious and does not pass from person to person.

Allergic reactions can occur at certain times of the year, as well as cause chronic complaints that continue throughout the year. Seasonal allergies are more frequent, especially in the spring, with increased pollen density.

What Are Allergy Symptoms?

Common symptoms of allergy include:

• Frequent and consecutive sneezing

• Transparent runny nose

• Nasal congestion

• Itching in the nose, eyes and throat

• Watering and redness in the eyes

• Genital discharge

• Mild cough

• Shortness of breath in some cases

Allergy usually does not show fever, intense muscle pain and severe weakness. This condition is an important clue in distinguishing flu and allergy.

Differences Between Flu and Allergy

1. The cause of occurrence is different

Influenza occurs due to a virus. Allergy, on the other hand, develops as a result of an overreaction of the immune system to environmental substances.

2. Flu Is Contagious, Not Allergy

Influenza can be easily transmitted through coughing, sneezing, and close contact. Allergies, on the other hand, do not pass from person to person.

3. The way symptoms start is different

Flu symptoms usually start suddenly. Allergy symptoms, on the other hand, can develop more slowly and persist as contact with the allergen continues.

4. Fever is Common in Influenza

High fever is common in flu, while allergies usually do not have fever.

5. Muscle Pain Is More Pronounced In Flu

With influenza, widespread muscle and joint pain is observed. In allergies, these complaints are usually not found.

6. Eye Itching May Signal Allergy

Itching, watering and redness of the eyes are quite common in allergies. With the flu, these symptoms are rare.

7. Duration of Symptoms May Vary

While flu usually resolves within 1 week, allergy symptoms can persist for weeks or even months.

When should I consult a doctor?

Some symptoms can be harbingers of serious health problems. It is imperative to contact a medical institution in the following cases:

• High fever that does not fall

• Shortness of breath

• Chest pain

• Severe and prolonged cough

• Blurred consciousness

• Symptoms of fluid loss in children

• Aggravation of symptoms in people with chronic diseases

Especially elderly individuals, pregnant women, children and people with weak immune systems are in the risk group.

Ways to Prevent Flu and Allergies

To Prevent Flu:

• Wash your hands frequently.

• Be careful in closed and crowded environments.

• Eat a balanced and vitamin-rich diet.

• Pay attention to your sleep pattern.

Get the flu vaccine according to the doctor's recommendation.

To Prevent Allergies:

• Try not to stay outdoors for a long time during times of high pollen density.

• Do house cleaning regularly.

• Keep items that retain dust to a minimum.

• Use brooms with HEPA filters.

• Limit contact if there is sensitivity to pet hair.

• Perform allergy treatment under the supervision of a doctor.

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