Multiple studies of children in developing countries found that zinc supplementation in malnourished children with acute diarrhea may reduce the severity and duration of diarrhea, especially in children with low zinc levels.

The healing process of gastric ulcers may be enhanced through treatment with zinc, although further studies will be needed to determine to which extent zinc may be beneficial for patients with this condition. Most studies report no or few adverse effects associated with its use.

There is strong scientific evidence to suggest that zinc may help manage or reduce symptoms of sickle cell anemia. Most of these studies reported increased height, weight, immune system function and testosterone levels, and decreased numbers of crises and sickled cells following zinc treatment.

Based on high quality studies, topical or systemic use of zinc seems to be a safe and effective treatment for acne vulgaris; however some studies report no or negative effects of zinc. Additionally, many studies used combination treatments.Several studies identify a positive correlation between serum zinc levels and severity of acne, however others did not, and it remains to be determined to which degree internal zinc levels may correlate with the severity of acne.

One study has shown a correlation between low serum free fatty acids and zinc serum levels in children with attention deficit hyperactivity disorder. Two other studies found that zinc supplements reduced hyperactive, impulsive and impaired socialization symptoms, but did not reduce attention deficiency symptoms. Zinc supplementation may be a more effective treatment for older children with higher body mass index (BMI) scores.

In several studies, zinc supplements seemed to counteract hypothyroidism and slightly reduce the number of infections in children with Down's syndrome. However, zinc did not seem to improve depressed immune systems. Additional human research is needed before a firm conclusion can be made.

Evidence from two human trials suggests that zinc pyrithione shampoo may be an effective treatment for tinea versicolor fungal infections of the scalp. No side effects were noted. Additional research is needed before a strong recommendation can be made.

Lesser quality studies have been conducted to assess the effects of zinc (topical or taken by mouth) on herpes type I or II. Several of these studies used combination treatments or permitted the continued use of other medications, so the exact role of zinc in those studies is unclear. However, the positive results obtained in most trials suggest that zinc may represent a safe and effective alternative treatment for herpes type I and II, and should encourage further research into the topic using well-designed studies.

Zinc may improve serum cholesterol levels in hemodialysis patients. There is some evidence that zinc may improve cholesterol ratio of HDL "good cholesterol" versus LDL "bad cholesterol" which would be considered a positive effect. Well-designed clinical trials are needed before a recommendation can be made.

Zinc appears to be an essential trace element for the immune system, but research on the effect of zinc supplementation on immune function is scant and mostly focuses on patients with specific diseases. Zinc gluconate appears to exert beneficial effects on immune cells, improving CD3 and CD4 counts and increasing CD4/CD8 ratios in children. There are relatively few studies that examine zinc levels and the effects of zinc supplementation on the health of the elderly population. Further research is needed before a recommendation can be made.

A few studies have reported significant reduction in plaque accumulation following treatment with zinc rinses and dentifrices. Preliminary research suggests that zinc citrate dentifrice may reduce the severity and occurrence of supragingival calculus formation. However, more well-designed studies are needed to confirm such benefits. More research might help to determine zinc's potential efficacy in other dental applications.

Wilson's disease is an inherited disorder of copper metabolism characterized by a failure of the liver to excrete copper, leading to its accumulation in the liver, brain, cornea, and kidney, with resulting chronic degenerative changes. Preliminary research suggests that zinc treatment may be effective in maintenance of Wilson's disease. Relatively few cases of adverse effects have been reported, including one case report presenting a fatality, however, it is unclear whether or not the death was caused by zinc. Several studies have been conducted by the same authors, resulting in possible bias. More well-designed trials are needed to confirm these early results.

A few studies that examined the efficacy of zinc in treating alopecia report contradictory results. Additional information is needed before a conclusion can be made.

Reports of zinc's effectiveness in treating symptoms of anorexia nervosa, observed in young adults are based on small, non-randomized studies, but all agree on the beneficial effects of zinc. Well-designed trials with a larger number of participants are needed to confirm these results.

Chewing gum containing zinc seemed to reduce bad breath (halitosis) in preliminary study.

One small study notes that children with beta-thalassemia who took oral zinc supplements for one to seven years increased in height more than those who did not take zinc. Additional information is needed to confirm these findings.

In one study, patients with recurrent boils (furunculosis) treated with zinc found their furuncles did not reappear. Well-designed clinical trials are needed to confirm this potential benefit.

Study results of zinc sulfate supplements given to burn victims to increase healing rate yield mixed results. Further research is needed before a recommendation can be made.

One study suggests that zinc supplements taken with antibiotics may be more effective than antibiotics alone in reducing pain, urinary symptoms, quality of life and maximum urethra closure pressure for patients with chronic prostatitis. Further research is needed to confirm these results.

One poorly designed study indicates that zinc supplementation may enhance neurological recovery in patients with closed head injuries. Further research is needed to confirm these results.

One study indicates that daily supplementation with zinc may be of limited usefulness for improving cognition in lead-exposed schoolchildren. Further study may be warranted in this area.

There are contradictory results regarding the efficacy of zinc formulations in treating duration and severity of common cold symptoms. Although zinc might be beneficial in the treatment of cold symptoms, more studies are needed to clarify which zinc formulations may be most effective, which rhinoviruses are affected by zinc, and if nasal sprays provide a useful alternative application route for zinc treatment. A recent study found no significant differences between zinc nasal spray and placebo.Negative results may be the cause of too using doses of zinc that are too low or the presence of compounds like citric or tartaric acid, which may reduce efficacy due to chelating of the zinc ion.

Preliminary research of zinc supplements in patients with Crohn's disease has yielded positive results. Well-designed clinical trials are needed to confirm these results.

Shampoo containing 1% of zinc pyrithione has been shown to reduce dandruff in some people.

Diabetic patients typically have significantly lower serum zinc levels compared with healthy controls. Based on one randomized, controlled trial, zinc supplementation for type-2 diabetics may have beneficial effects in elevating their serum zinc level, and in improving their glycemic control that is shown by decreasing their HbA1c% concentration. Further study is needed before a recommendation can be made.

Oral zinc supplementation may improve glycemic control and severity of peripheral neuropathy. Further research is needed before a recommendation can be made.

Zinc may reduce the incidence of diaper rash and have a preventative effect.

There is conflicting data regarding the correlation of zinc serum levels and eczema. One study noted zinc might have caused an increase in itching after several weeks of supplementation. Additional information is needed to help clarify these results.

Zinc may improve exercise performance in athletes with low serum zinc or zinc deficiencies. Additional evidence is needed before a recommendation can be made.

Gilbert's syndrome is a common, often inherited disorder that affects processing by the liver of the greenish-brown pigments in bile (called bilirubin). The resulting abnormal increase of bilirubin in the bloodstream can lead to yellowing of the skin (jaundice) but the liver itself remains normal. It is more common in men than women and is named after a French gastroenterologist. Zinc sulfate supplementation seemed to decrease serum unconjugated bilirubin levels in a small study. Well-designed clinical trials are needed to confirm these results.

Hepatic encephalopathy is abnormal brain function caused by passage of toxic substances from the liver to the blood. Three small randomized, double-blind trials of zinc for this indication have yielded conflicting results.

Two studies have shown that zinc in combination with interferon or interferon and ribavirin for hepatitis C viral infection patients did not show significant benefits, except for lower incidence of gastrointestinal side effects in one study. Further study may be warranted in this area.

Patients with HIV/AIDS, especially in those with low zinc levels, may benefit from zinc supplementation. Some low quality studies cite reduction in infections, enhanced weight gain and immune system function, including increased CD4 and CD8 cells. However, other low quality studies conflict with these findings. Further research is needed before a conclusion can be drawn.

Although zinc is frequently cited as having beneficial effects on incision wound healing, few studies have investigated this use. Further research is needed before a recommendation can be made.

Many studies report beneficial results of zinc supplements on infertility, as expressed in improved sperm quality and number, although this effect may depend on the cause of infertility. A minor increase in abnormal spermatozoa in subfertile males taking zinc was noted in one study. Additional information is needed before a firm conclusion can be drawn.

Preliminary study shows a potential improvement in uremic patients taking zinc supplements. Further research is needed to confirm these results. Zinc supplementation may be recommended only in the patients with proven zinc deficiency, but for all chronic renal failure patients it is questionable.

Short-term zinc supplementation may increase weight gain and decrease infections, swelling, diarrhea, anorexia and skin ulcers in children with extreme malnourishment.

There are conflicting findings regarding the potential benefit of zinc for healing leg ulcers. All studies, however, reported no or few adverse effects.

A few studies have examined the efficacy of zinc treatment in leprosy. Studies of zinc taken by mouth report positive results, while one study of topical zinc reports negative results. Further research is needed before a conclusion can be drawn.

People with alcoholic liver cirrhosis may be deficient in zinc. Preliminary studies suggest that zinc may benefit these patients. Further evidence is needed to confirm these findings.

Results from large clinical trials suggest that supplementation with zinc may reduce the incidence of lower respiratory infections. Some studies suggest these effects to be only apparent in boys, and not girls. A trend toward increased respiratory infections in children has been noted in one study. A recent study does not support the use of zinc supplementation in the management of acute lower respiratory infections requiring hospitalization in indigenous children living in remote areas. Due to conflicting results, further research is needed before a conclusion can be drawn. Future studies could examine whether these adult populations have a similar response.

Most studies examining the relationship between dietary zinc intake over many years and macular degeneration have not reported positive correlations. However, one large well-designed, randomized study, which examined the efficacy of zinc supplements in preventing loss of visual acuity, found zinc supplements to be beneficial in preventing the occurrence of age related macular degeneration. Since study results are conflicting, additional well-designed clinical trials are needed before a recommendation can be made.

Results are contradictory for the effect of zinc on malaria symptoms. Some randomized, double-blind clinical trials suggest no effect of zinc supplementation on the severity of malaria. Other studies suggest that zinc supplementation may reduce the number of stays in hospital and death rate due to P. falciparum infection. Further well-designed, randomized and controlled trials are required to address these discrepancies.

The results of one case series suggest that zinc supplementation may improve muscle cramps in patients with cirrhosis. Further research is needed to confirm these results.

In a few studies of varying quality, patients with cutaneous leishmaniasis were injected with zinc sulfate intralesionally. One study found zinc sulfate was better than meglumine antimoniate for the first four weeks, but no statistical differences were observed after six weeks. Zinc may decrease the severity of infection and re-infection of S. mansoni , but does not seem to prevent initial infection. More research should be done in this area to examine how zinc affects the S. mansoni life cycle and whether this data can be extrapolated to other species of Schistosoma .The effects of zinc on the rate of parasitic re-infestation have been examined in children. No significant effect of zinc treatment was found. Due to conflicting results in this area, more research is needed before zinc can be recommended for the treatment of parasites.

Results from one study show that a combination of spirulina extract plus zinc may be useful for the treatment of chronic arsenic poisoning with melanosis and keratosis. More research is needed to confirm the effects of zinc alone.

According to one review, there is no evidence to suggest that zinc supplementation offers benefits during pregnancy, although there is a possible reduction in labor complications and pre-term deliveries. However, results from individual studies suggest a possible benefit of zinc supplementation on blood pressure during pregnancy. Further research is needed before a conclusion can be drawn.

There are only a few studies that examine the efficacy of zinc treatment on symptoms of psoriasis, including psoriasis induced arthritis-like symptoms. One trial noted a reduction in pain and joint swelling. Other studies do not support a role for zinc in alleviating the symptoms of psoriasis. Further, well-designed clinical trials are required to clarify these results.

Radiation has the potential side effect of mucositis, which is inflammation of mucous membranes inside of the mouth, nose and throat. Two trials suggest that zinc may lower the degree of mucositis in patients on radiation. Further research is needed to confirm these results.

The majority of trials do not show significant improvements in arthritis symptoms following zinc treatment. Interpretation of some data is difficult by because patients in the studies were permitted to continue their previous arthritis medication and most studies used a small number of participants. Well-designed clinical trials are needed before a decision can be made.

Preliminary evidence suggests that topical zinc oxide oil may help manage perianal and buttock skin damage in incontinent patients. Further research is needed to confirm these results.

Zinc sulfate has been studied for the treatment of recurrent aphthous stomatitis (RAS). Study results conflict and no clear conclusion can be drawn at this time.

Results from studies investigating the potential role of zinc in treating taste and smell disorders are contradictory. Well-designed research is needed to determine if zinc contributes to the treatment of taste and smell disorders.

Studies on the efficacy of zinc in treating tinnitus yield contradictory results based on subjective findings. Further research is necessary before a conclusion can be drawn.

Little research is available on the efficacy of zinc for the treatment of trichomoniasis, a sexually transmitted disease (STD). One very small study suggests that a zinc sulfate douche and the prescription antibiotic metronidazole may effectively treat patients with recalcitrant trichomoniasis. However, more well-designed human studies are necessary before a firm conclusion can be drawn.

One study suggests that zinc sulfate may be an efficacious therapy option for recalcitrant viral warts. Well-conducted studies are needed to confirm these early results.

In a very small study, oral zinc supplements did not seem to improve the clinical condition of patients with unresponsive celiac syndrome.

In a small study, zinc supplementation did not seem to have a beneficial effect on symptoms of patients with chronic inflammatory rheumatic disease.

Zinc supplementation did not improve the nutritional status in patients on CAPD based on one well-designed trial.

Zinc supplementation does not seem to affect clinical status, growth velocity or lung function in children with cystic fibrosis.

One small study found that zinc supplementation does not seem to improve inflammatory bowel disease.

One study found that zinc supplementation does not seem to lessen the duration of tachypnea, hypoxia, chest indrawing, inability to feed, lethargy, severe illness, or hospitalization in children.