The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.
Zinc oxide allergy has been reported. Avoid with known allergy or hypersensitivity to zinc compounds.
Side Effects and Warnings
Zinc is regarded as relatively safe and generally well tolerated when taken at recommended doses, and few studies report side effects. Occasionally, adverse effects such as nausea, vomiting, or diarrhea have been observed. Reduced levels of high-density lipoprotein (HDL), or "good," cholesterol have been observed following daily supplementation with zinc. Reduced immune responses have also been observed. A slight tingling or burning sensation in the nostril has been reported from zinc nasal gel. A trend toward increased respiratory infections in children has been noted. One case of hypersensitivity pneumonitis has been reported.
Unpleasant taste, taste distortion, and abdominal cramping have been occasionally reported, especially in studies examining the efficacy of zinc-containing lozenges in treating symptoms of common cold or treatment of diarrhea in children.
Reports of skin conditions have been noted. In one study, worsening of an acne condition was observed following topical application of zinc, although many studies have shown positive effects of zinc on acne. A case report suggested the presence of dermatitis due to zinc deficiency.
Use amounts regularly exceeding the recommended upper tolerance levels (greater than 40 milligrams daily) under a physician's guidance only. Sideroblastic anemia, leukopenia, microcytic anemia, neutropenia, bleeding gastric erosion, hepatitis (liver inflammation), liver failure, intestinal bleeding, acute tubular necrosis, and interstitial nephritis have been reported following the ingestion of large amounts of zinc. High-quality studies have found evidence of an association between high-dose zinc supplement use and hospitalization for urinary complications, including benign prostatic hyperplasia or urinary retention, urinary tract infection, and urinary lithiasis. This was especially evident among males.
There is one report of death following the ingestion of 400 coins (mostly pennies). Pennies are composed mostly of zinc. There is also one case report of a fatal outcome from cystic degeneration in the putamen and necrosis in the hypothalamus. It was reported as a consequence of zinc treatment for Wilson's disease. However, the patient had received penicillamine, followed by a relatively high daily dose of zinc for several weeks, followed by penicillamine again for an unspecified time, so it remains unclear if zinc was responsible for the death.
Zinc may increase the risk of bleeding. Caution is advised in patients with bleeding disorders or those taking drugs that may increase the risk of bleeding. Dosing adjustments may be necessary.
Zinc may lower blood sugar levels. Caution is advised in patients with diabetes or hypoglycemia, and in those taking drugs, herbs, or supplements that affect blood sugar. Blood glucose levels may need to be monitored by a qualified healthcare professional, including a pharmacist, and medication adjustments may be necessary.
Use cautiously in patients with high cholesterol or blood fats, a high risk of developing heart disease, various skin disorders, gastrointestinal disorders, liver disease, genitourinary conditions, blood disorders, neurological disorders, pulmonary or respiratory disorders, immune disorders, or kidney disease, or in patients taking antidepressants, potassium-sparing diuretics, antibiotics (particularly tetracyclines and quinolones), iron, penicillamine, thyroid hormones, or copper.
Avoid in patients who are homozygous for hemochromatosis (a metabolic disorder involving the deposition of iron-containing pigments in the tissues and characterized by bronzing of the skin, diabetes, and weakness).
Avoid use of intranasal Zicam®. Numerous reports exist of loss of smell associated with zinc-containing Zicam® products. These zinc-containing formulas have since been withdrawn from the U.S. market.
Avoid with known allergy or hypersensitivity to zinc compounds.
Pregnancy and Breastfeeding
Zinc is likely safe when consumed in amounts generally found in foods (or as part of a multivitamin or multimineral compound) in nonallergic women. There is insufficient reliable information available about the safety or efficacy of medicinal use of zinc during pregnancy or lactation. The relationship between zinc levels or intake and low birthweight or delivery complications has been studied, but the results are conflicting.
The recommended daily allowance (RDA) for zinc during pregnancy and lactation is as follows: for pregnant women 19 years old and older, 11 milligrams daily; for pregnant women 14-18 years of age, 13 milligrams daily; for breastfeeding women 19 years old and older, 12 milligrams daily; and for breastfeeding women 14-18 years of age, 14 milligrams daily.