Ragweed and old' Rover have one thing in common: if you're allergic, they can trigger any number of reactions ranging from a congested, runny nose to red, swollen eyes. It's probably not even the dog's fault, just the hair that he sheds. Many people who are allergic to dogs can tolerate certain species such as poodles, which hardly shed at all. Allergic children who want a pet should consider fish. Pollen is another matter. Certain trees, grasses and weeds send out their pollen every year like clockwork, and as long as you breathe, you're susceptible. You can be sure that if your pet goes outdoors it will collect pollen on its fur and carry it indoors. If you get close to your pet's hair you're likely to feel the same effect. Some commercial medicines can relieve allergic symptoms for a short period of time, but the only long-lasting remedy is a visit to an allergy specialist. Through a series of tests, the exact nature of your allergies can be determined. The doctor can then begin treatment by desensitizing your system to the particular allergens. There are two good things about this method of treatment. It lasts for a long time, and you can keep your pet.