From WebMD

1. Pollen -- Exposure to pollen from trees, grasses, and weeds can trigger hay fever or seasonal allergies. Symptoms include sneezing, runny nose, nasal congestion, and itchy, watery eyes. Treatments include over-the-counter products, prescription drugs, and allergy shots. Prevent symptoms by staying indoors on windy days when pollen counts are high, closing windows, and running the air conditioning.
2. Animal Dander -- Proteins secreted by oil glands in an animal's skin and present in their saliva can cause allergic reactions for some. The allergy can take two or more years to develop and symptoms may not subside until months after ending contact with the animal. If your pet is causing allergies, make your bedroom a pet-free zone, avoid carpets, and wash the animal regularly. A HEPA filter and frequent vacuuming may also help. Allergy shots may be beneficial.
3. Dust Mites -- Dust mites are microscopic organisms that live in house dust. They thrive in areas of high humidity and feed on the dead skin cells of humans and their pets, as well as on pollen, bacteria, and fungi. Help prevent dust mite allergies by covering mattresses, pillows, and box springs, using hypoallergenic pillows, washing sheets weekly in hot water, and keeping the house free of dust collecting-items such as stuffed animals, curtains, and carpet.
4. Insect Stings -- People who are allergic to stings can have a severe or even life-threatening reaction. Symptoms include extensive swelling and redness from the sting or bite that may last a week or more, nausea, fatigue, and low-grade fever. Rarely, insect stings may cause anaphylaxis, with symptoms including difficulty breathing, hives, swelling of the face, throat, or mouth, rapid pulse, dizziness, or a sharp drop in blood pressure. For those severely allergic, epinephrine should be administered immediately after a sting; allergy shots are recommended to prevent anaphylaxis with future stings.
5. Molds -- Molds produce allergens, irritants, and in some cases, potentially toxic substances. Inhaling or touching mold or mold spores may cause allergic reactions in sensitive individuals. There are many types of mold; all need moisture to grow. They can be found in damp areas such as basements or bathrooms, as well as in grass or mulch. Avoid activities that trigger symptoms, such as raking leaves. Ventilate moist areas in the home.
6. Food -- Milk, shellfish, nuts and wheat are among the most common foods that cause allergies. An allergic reaction usually occurs within minutes of eating the offending food. Symptoms, which can include asthma, hives, vomiting, diarrhea, and swelling around the mouth, can be severe. Avoid offending foods altogether; but if exposed, treatment with antihistamines or steroids is recommended. In life-threatening situations, an epinephrine injection is needed.
7. Latex -- Latex in gloves, condoms, and certain medical devices can trigger latex allergy. Symptoms include skin rash, eye irritation, runny nose, sneezing, wheezing, and itching of the skin or nose. Allergic reactions can range from skin redness and itching to anaphylaxis, a serious reaction which can cause difficulty breathing, hives, and sudden gastrointestinal problems. Those allergic should wear a MedicAlert bracelet and carry an epinephrine kit.
8. Medication -- Symptoms of allergies to medications, such as penicillin or aspirin, can range from mild to life-threatening and can include hives, itchy eyes, congestion, and swelling in the mouth and throat. It's best to avoid the drug altogether; however, if exposed, treatment with antihistamines or steroids is recommended. For coughing and lung congestion, bronchodilators may be prescribed. For severe symptoms, epinephrine may be needed.
9. Fragrance -- Fragrances found in products including perfumes, scented candles, laundry detergent, and cosmetics can have mild to severe health consequences. For most people, symptoms abate once the scent is out of range. For some, repeated exposures cause an increase in symptoms that occur more often and last longer. There’s some debate as to whether fragrance reactions are a true allergy or simply a response to an irritant.
10. Cockroaches -- Ick! Not only are cockroaches creepy, but a protein in their droppings can be a troublesome allergen. It can be difficult to eradicate cockroaches from your home, especially in a warm climate, or if you live in an apartment building where bugs can pass back and forth to a neighboring unit. Treat for roaches by using pesticides, keeping a clean kitchen, and repairing cracks and holes in floors, walls, and windows to prevent their entry into the home.