It can be so hard to tell a summer cold from an allergy that even doctors have a tough time. One rule San Francisco pediatrician Eileen Aicardi, MD, goes by in children is their age. “Before age two, I often suspect a cold, but after age two, when environmental allergies first begin to show up in kids, it gets much trickier.”

Since that leaves roughly 76 years of confusion after age two, it’s helpful to know which symptoms tend to indicate a cold and which signal an allergy.

Colds are caused by viruses, which are carried to the back of the throat and deposited near the tonsils. The body responds by releasing a "good guy" compound called histamine to fight off the invader. Environmental allergies, on the other hand, are set off when the body’s immune system sends out an alarm over a substance such as pet dander, dust or pollen. Once again histamine roars to the rescue, but now it's the bad guy — the inflammation it triggers makes us miserable. Histamine, in fact, is responsible for the allergy symptoms we know and hate.

Related: Ban These 7 Allergens from Your Home

While Aicardi and other doctors say there is no surefire way to distinguish a summer cold from an allergy, there are a few questions that can help you tell the difference.

Did your symptoms feel like they had a beginning, middle and end? Colds tend to feel that way, and come on in stages, while allergies tend to be fairly constant and unchanging. Aicardi says that with a cold, congestion often marks the first week, followed by a residual cough the second week.

Did you have the same symptoms about this time last year? Aicardi recommends that parents and patients track cold and allergy symptoms on their cell phone for a year or two to look for a pattern. If your symptoms tend to show up the same time of year, you may be having an allergic reaction to hay fever or pollen.

Did Benadryl or another antihistamine ease your symptoms? Doctors look at whether an over-the-counter remedy helps relieve symptoms to help diagnose colds and allergies. This used to be harder when drug companies tended to include antihistamines (for allergies) and decongestants (for colds) in the same product to “cover all the bases,” says Aicardi. Pure decongestants such as Sudafed usually won’t help with allergies, but pure antihistamines such as Benadryl usually will.

Are you achy? Do you have a low grade fever? These tend to be symptoms of a cold, not allergies.

Have your kids done “the allergy salute”? Rima Rachid, MD, director of allergen immunotherapy at Boston Children’s Hospital, says she finds that kids often press their noses upward with the palm of their hand to relieve itchiness. Sometimes kids develop a small crease at the bridge of the nose from doing this over and over again.

Related: Achoo! Three Ways to Treat Springtime Allergies

What your runny nose means

Both colds and allergies can involve a runny nose. Doctors used to tell patients that thick, yellow mucus indicates a cold and that clear, watery mucus signifies allergies. But that theory doesn’t always hold. One reason? “A sinus infection that has been caused by allergies can have a thick mucus like a cold does,” says Aicardi.

Perhaps most confusing, you may have an allergy and soon afterward experience symptoms of a cold, such as sinus congestion. Why? The sinuses often become infected with bacteria as you rub your nose.

Symptoms of a sinus infection include tightness or a congested feeling around the face, especially between the eyes. You may also notice that your teeth ache. See a doctor if you develop these symptoms.

Fighting off allergies and colds

If you’re suffering from unpleasant allergy symptoms, your doctor may prescribe an OTC or prescription antihistamine or a steroid nasal spray, along with advice to avoid the offending substance, according to the Mayo Clinic. Common allergens include dust, pollen and mold. Allergy testing may be helpful if you’re not sure what you’re allergic to.

Related: Seasonal Allergies: Yes, They’re Getting Worse, and Here’s Why

Antibiotics don’t work against viruses, and the common cold is usually harmless, so doctors typically advise that you rest and wait it out. You should see a doctor if you have a fever over 103 degrees F; a fever with chills and thick mucus; a cold along with severely swollen glands; or severe sinus pain, according to the Mayo Clinic.

Children are often hit harder by colds and may develop painful earaches. The Mayo Clinic advises you to see a doctor if your child:

  • Is three months old or younger and has a fever of 100.4 F
  • Has a fever that keeps jumping above 104 F
  • Is dehydrated or urinating less than usual
  • Is 2 or younger and has a fever lasting more than 24 hours
  • Is older than 2 and has a fever for three days or more
  • Vomits or complains of abdominal pain
  • Has a severe headache or a stiff neck
  • Is unusually sleepy
  • Has difficulty breathing
  • Cries inconsolably
  • Can’t stop coughing

Related: Allergy Relief for Your Child

Kathryn Olney is a freelance writer and editor who has served as a reporter and editor for California, San Francisco and Mother Jones magazines.