As you probably already know, molds are something you should stay away from. Inhaling or touching them can cause immediate or delayed symptoms, including sneezing, runny nose, red eyes and skin rash. Exposure to mold can even affect non-allergic people, irritating the eyes, skin, nose, throat and lungs.

Mold reproduces through tiny airborne spores. When they land on a wet surface, mold can start to grow indoors. Since mold needs moisture to survive, the trick is to keep your home dry. Places to guard against mold are: basements, closets, bathrooms, shower stalls, refrigerator drip trays, house plants, humidifiers and garbage pails.

Animal allergies are very common. However, many people don't know what triggers the allergy. Most think it's the fur. The major culprit is the saliva that sticks to the fur when your pet cleans itself. The saliva contains a protein that causes a reaction. Cats can be worse than dogs because they lick themselves more often, and spend more time in the house.

Allergy-causing proteins can also come from your pet's urine. This explains why some people are allergic to guinea pigs, gerbils and other rodents.

A pet allergy can take more than 2 years to develop, and may not show signs of improvement until 6 months after the animal has stopped living with you. Pet allergens can remain in carpet and furniture for 4 to 6 weeks, and can linger in the air for months. So before you move into a new house or apartment, find out if a pet has been living there.

Even though you may not always see them, depending on where you live in the US, chances are dust mites are all over your house. They thrive in bedding, upholstered furniture, and carpets. These tiny creatures are perhaps the most common cause of perennial allergies and can trigger symptoms similar to pollen allergy.

And even though they're microscopic, they're not completely invisible. Those particles you see floating around in a shaft of sunlight? Some of them are actually dead dust mites and their droppings. The proteins in the droppings are what cause the allergic reaction.

Cockroaches live all over the world, from tropical areas to the coldest spots on earth. Cockroach allergen is believed to derive from feces, saliva and the bodies of these insects. Cockroach allergen particles are large and settle rapidly on surfaces. They become airborne when the air is stirred by people moving around or by children at play. People with chronic severe bronchial asthma are most likely to have cockroach allergy. Also likely to have it are people with a chronic stuffy nose, skin rash, constant sinus infection, repeat ear infection and asthma.

Although more than 1,000 species of grass grow in North America, only a few produce highly allergenic pollen. That's small comfort if you're one of the millions of people affected by grass pollen. The most commons grasses that can cause allergies are Bermuda grass, Johnson grass, Kentucky bluegrass, Orchard grass, Sweet vernal grass, Timothy grass.

If you are allergic to grass pollen and have a grass lawn, have someone else do the mowing. If you must mow the lawn yourself, wear a mask. Keep the grass cut short. Consider ground covers that don't produce much pollen, such as Irish moss, bunch and dichondra. You should remember that pollen can also be transported indoors on people and pets, so vacuum frequently.

When you think seasonal allergies do you think tree pollen? You should. Tree pollen is one of the worst allergy offenders. First, it has a jump on all other pollen producers. In the South, for example, trees start releasing their pollen as early as January. What's more, trees produce light, dry pollen that can be carried by the wind for miles.

Fortunately, fewer than 100 species (out of 50,000) are known to cause allergies. Some common examples include: elm, sycamore, hickory, walnut, pecan.

In certain species, it's only the male tree that causes problems. Their female counterparts are completely pollen-free. Poplar, cottonwood, box elder, red maple, silver maple, willow, ash, date palm and Phoenix palm trees all fall into this category.

Though less common, it is possible to be allergic to more than one tree. Some people have cross- reactions to trees in the alder, beech, birch and oak families, as well as the juniper and cedar family.

We all know weeds. They multiply fast. But did you also know they're the most prolific producers of pollen. Ragweed is by far the biggest troublemaker. A single ragweed plant can produce a million grains of pollen a day. Yes, a million. But there are plenty of other high-producing allergenic plants: sagebrush, redroot pigweed, lamb's quarters, Russian thistle (aka tumbleweed) and English plantain.

The season for ragweed pollen runs from August to November, but mid-September can be the worst time, when pollen levels peak. Also, be aware that pollen counts are at their highest between the hours of five and ten a.m. Another thing to keep in mind: allergies can be aggravated by dry, hot and windy conditions.

Mold. Dander. Dust. (The list of potential indoor allergens goes on and on and on. While everyday substances like these are generally harmless; they can trigger a reaction in a person with allergies. Histamine and other chemicals are released, causing itching and swelling, mucus production and, in some cases, hives and rashes. Symptoms vary in severity but most affect the skin, eyes or one's breathing.

Did you know that millions of people suffer from seasonal allergies blame it on plant pollen? But, it's not the only source of outdoor allergens and not all plant pollen is bad. Furthermore, it's not always obvious which plants are giving you trouble. Ragweed, for example, is one of the nature's most prevalent allergens. Nevertheless, it's often overlooked because of its tiny flowers. Instead, people assume that they're sniffling and sneezing because of the more flowery goldenrod that blooms at the same time.

Plant pollen can trigger severe symptoms. However, it's not the only source of outdoor allergens. There are also many forms of molds and mildews that affect people all year. Air pollution, as well as dry, windy weather conditions, can also aggravate allergies. And the greater the exposure to allergens, the worse the reaction.