I am a teenager, but often catch a cold

Condition analysis:
If you snot is clear, then I guess you are suffering from rhinitis.

Instructions:
Allergic rhinitis is an allergic reaction that happens when your immune system overreacts to substances that you inhale, such as pollen. The two types of allergic rhinitis are:
Seasonal allergic rhinitis (hay fever)
Perennial allergic rhinitis, which occurs year-round

Symptoms of allergic rhinitis are similar to cold symptoms. But they are not caused by a virus the way a cold is. When you breathe in an allergen, your immune system springs into action. It releases substances known as IgEs into your nasal passages, along with inflammatory chemicals, such as histamines. Your eyes may itch or your nose and sinuses may become itchy and congested. Scientists are not sure what causes your immune system to overreact to allergens. Allergic rhinitis can cause many symptoms, including: stuffy or runny nose, sneezing, post-nasal drip, red, itchy, watery eyes, swollen eyelids, itchy mouth, throat, ears, and face, sore throat, dry cough, headaches, etc.

Treatment
The best way to reduce symptoms of allergic rhinitis is to prevent exposure to allergens. Drugs such as antihistamines, decongestants, and nasal corticosteroid sprays may help control allergy symptoms. Some complementary and alternative therapies may also be used to treat the symptoms. Your doctor may recommend immunotherapy, or "allergy shots." With this treatment, you receive regular injections of an allergen, with each dose being slightly larger than the previous dose. Your immune system should gradually get used to the allergen so that it no longer reacts to it.

Lifestyle
Get rid of carpets and upholstered furniture.
Wash bedding every week in very hot water.
Keep stuffed toys out of the bedroom.
Cover pillows and beds with allergen-proof covers.