Histamines tell your tissues to secrete fluids that make them irritated. That's when allergy symptoms occur. If your allergies are worse in some seasons than others, there's a good possibility you're allergic to pollen. Plants pollinate at different times of the year and it varies from season to season. Also, an early spring and late summer can be very problematic depending on where you live.
Allergies are tricky because no two people suffer the same.
That is why they are hard to treat. You may be allergic to more then one thing. This is known as Perennial Allergen because it doesn't change with the seasons. The possible culprits include animal dander, dust mites, mold, feathers and dust. For example, you could be allergic to pollen in the spring and dust mites in the winter.