Sniffing out an allergy can be tricky.

Here are some clues to consider:- Allergic "shiners": Dark, swollen bags under the eyes are common in allergies, rare in colds and flu.

- Irritated red, itchy or watery eyes: Allergies cause these symptoms, especially itching, much more often than colds and flu.

- Sneezing: Rarely with flu; sometimes with colds; often with allergies.

- Fever, chills, muscle aches: Rare in allergies; common in colds and flu.

- "Allergic salute": Frequent, upward rubbing of the nose, which also occurs with colds, may signal allergies if it lasts more than two weeks. May lead to an "allergic crease" at the bridge of the nose.

- Runny nose: Allergy discharge is usually thin, clear and watery. With a cold or flu, the mucus often is thick and yellowish or greenish.

- Clucking: Scratching of the roof of the mouth with the tongue occurs almost exclusively in allergic kids.