By Stephanie Stahl

PHILADELPHIA (CBS) — Feeling like you might have a cold? Maybe not. Welcome to ragweed season, and the allergy alert is high.

About 23 million Americans have ragweed allergies. The sniffles that come with allergies are also symptoms of a cold. Scientists say there are a few key differences.

The Philadelphia skyline is clear from the Art Museum steps. It’s what you can’t see — ragweed pollen in the air — that’s triggering allergy symptoms.

Those symptoms — congestion and sneezing — can also be signs of a cold. Itching is a often a telltale sign of allergies.

“Because of the way allergy cells work when they’re activated, they secrete itchy chemicals, so that’s one way — sort of a rule of thumb allergy is present, as opposed to a viral infection or a cold is how itchy are you?” Dr. Alice Hoyt, with the Cleveland Clinic, said.

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In addition to feeling itchy, ragweed allergies also cause watery eyes and symptoms can last for a long time. Colds usually last one to two weeks.

Ragweed season generally lasts from mid-August until the first frost.

Over-the-counter allergy products can often help relieve symptoms. A sterile saline spray is helpful for rinsing pollen and mucus out of the nose.

Also over-the-counter nasal steroid sprays can reduce allergic inflammation and there are medications formulated specifically for allergies.

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“An over-the-counter antihistamine and we recommend the newer antihistamines because they’re less sedating than some of our older antihistamines,” Hoyt said.

With people outside enjoying a beautiful day on Kelly Drive, scientists say ragweed has become excessive mainly because of extreme weather — high temperatures and heavy rain — that creates the perfect environment for ragweed.

As a result, the allergy season becomes longer and more brutal.

For people with severe allergies, allergy shots and immunotherapy tablets can provide more long-term ragweed relief.

Stephanie Stahl