TCM considers allergies or hay fever a manifestation of Wind invading the upper body. This occurs because one's protective Qi has been weakened. The goal is not only to treat one's acute symptoms and provide immediate relief, but to treat any underlying immune system imbalances, which may be the real cause of one's allergy problems.
Such treatments may take the form of acupuncture and revising one's diet, including the addition of specific herbal formulas. Building up your immune system through diet and/or supplements builds the protective Qi.
There are many holistic Chinese herbal formulas that TCM practitioners use to treat allergies. In most cases, once an allergy has been identified, it is best to start treatment before the symptoms manifest.