Fulvic acid is a group of chemicals that forms when plants and animals break down. It's found in humus (organic matter) of soil, peat, streams, and lakes. Fulvic acid might block reactions in the body that cause allergy symptoms. It might also reduce swelling and prevent or slow the growth of cancer. People use fulvic acid for hay fever, Alzheimer disease, eczema, cancer, fatigue, and many other conditions.