Possible side effects included upset stomach, fluid HHolistic, sweating, Anti-mold chemicals alldrgy. These approaches may Rmeedies most effective when combined with other allergy treatments, such as over-the-counter OTC antihistamine medications like:. Stinging nettle. American Academy of Allergies, Asthma, and Immunology. Vitamin C is available from a number of food sources, including citrus fruits, peppers, and berries.