hand sanitizer to stop contagious diseases

Are Allergies Contagious?

Unlike colds, flu, and other infections, allergies aren’t contagious.

The cause of allergies is not a virus or bacteria, but an overactive immune system. In case of an infection, the immune system fights a microbe that is harmful and causes diseases.

In the case of allergies, the immune system reacts to a harmless substance, like pollen or cat dander, as if it is harmful.

However, certain infections mimic allergies. That’s why it is important to know the symptoms, so you know whether it’s allergies or an infection. A doctor can further help you with a diagnosis and provide treatment.

Some people may actually have a cold or an allergy, yet have no symptoms. Others will have only a few symptoms, others more. Some will have mild forms, while others will have severe reactions.

woman sneezing from contagious allergies

Allergy vs Cold and Flu

Allergies are not contagious, but colds and the flu are. Allergies, colds, and the flu may cause a stuffy, runny nose, sneezing, weakness and fatigue, headaches, and coughing.

Unlike allergies, colds could cause fever sometimes. Fever is a natural self-defense mechanism. An increased body temperature makes it harder for bacteria and viruses to survive.

A cold can often cause aches and pains, sore throat, yellowish or greenish nasal discharge, and perhaps some dizziness, too. A cold typically lasts about three to five days but could be up to 14 days.

In the case of the flu, a fever is even more likely to develop, and it can get high (100-102 F), especially in children. Headaches, as well as muscle pains and aches, are quite common. Coughs can be severe and associated with chest discomfort. There is an initial period of a few days of extreme exhaustion, followed by weeks of feeling weak.

Allergies are more likely to cause clear nasal discharge, itchy eyes and nose, scratchy throat, and wheezing. There is no presence of fever, aches, and pains, and headaches occur rarely. A congested nose and sneezing are the main symptoms of allergies. Chest discomfort is rare, and when it happens is usually due to allergic asthma.

medication to treat contagious colds and allergies

Allergy symptoms develop after exposure to an allergen and last for as long as the person is exposed. In the case of seasonal allergies, there will be a seasonal pattern, with symptom-free periods in between.

To treat colds and the flu, health professionals recommend plenty of rest and fluids. Decongestants and acetaminophen or ibuprofen are often used to relieve symptoms.

To treat allergies, it is important to avoid allergens. Medications to treat reactions include antihistamines, decongestants, and steroids.

When it comes to complications, colds and allergies can result in sinus or ear infections. These conditions can also worsen asthma. The flu may be complicated by bronchitis or pneumonia.

contagious stomach flu symptoms

Food Allergies vs Stomach Flu

Food allergies also aren’t contagious.

These allergies could be mistaken as stomach flu. Medically known as viral gastroenteritis, the stomach flu is very contagious. They both share similar symptoms, mostly affecting the digestive tract.

How can you tell the difference?

The typical symptoms of viral gastroenteritis include diarrhea, abdominal pain or cramping, nausea or vomiting, and fever. Both diarrhea and vomiting can be severe, causing significant dehydration.

Signs of dehydration include:

  • Extreme Thirst
  • Dry Mouth
  • Dark-Colored Urine
  • Extreme Weakness
  • Fatigue
  • Lightheadedness
  • Fainting

A person with stomach flu is contagious for up to 2 weeks from the first symptoms.

Contaminated food or water is often the source of infection. These viruses can live on surfaces like countertops for several weeks too.

How long do these symptoms last? Depends on the virus.

Most cases of gastroenteritis in the US are caused by norovirus, and the symptoms last about 1-3 days. Symptoms of infections with astrovirus also last about 1-4 days. Rotaviruses can cause symptoms for up to one week. Adenoviruses can cause symptoms for up to 2 weeks.

Food allergies, on the other hand, are not contagious. Your immune system reacts to certain proteins in the food.

The top 8 food allergens are found in:

  • Milk
  • Soy
  • Eggs
  • Wheat
  • Peanuts
  • Tree Nuts
  • Fish
  • Shellfish

In many cases, food allergies cause symptoms after eating foods you’re allergic to. Examples of these symptoms include abdominal pain, diarrhea, nausea, and vomiting.

Nasal congestion, wheezing, itchy skin, and hives can develop with food allergies, too. Tingling and itching of the mouth, swelling of the lips and face, dizziness, and lightheadedness are other possible symptoms.

There are also severe life-threatening allergic reactions that require emergency treatment. In this case, a person develops a swollen throat, difficulty breathing, sudden drop in blood pressure, rapid pulse, and may lose consciousness. In this instance, an EpiPen can treat the reaction.

Doctors can perform skin and blood tests to discover foods you’re allergic to.


While allergies are not contagious, they can mimic infections that are contagious and require a different treatment. This is why it is important to know the difference and similarities between allergy symptoms versus a contagious disease.

If you are not sure whether you’re experiencing an allergic reaction or an infection, seek medical advice. 

Your email address will not be published. Required fields are marked *