Dietary supplement
In most single-tablet, over-the-counter, daily vitamin and mineral supplements, zinc is included in such forms as zinc oxide, zinc acetate,  zinc gluconate, or zinc amino acid chelate.Generally, zinc supplement is recommended where there is high risk of zinc deficiency (such as low and middle income countries) as a preventive measure. Although zinc sulfate is a commonly used zinc form, zinc citrate, gluconate and picolinate may be valid options as well. These forms are better absorbed than zinc oxide. Gastroenteritis
Zinc is an inexpensive and effective part of treatment of diarrhea among children in the developing world. Zinc becomes depleted in the body during diarrhea and replenishing zinc with a 10- to 14-day course of treatment can reduce the duration and severity of diarrheal episodes and may also prevent future episodes for as long as three months. Gastroenteritis is strongly attenuated by ingestion of zinc, possibly by direct antimicrobial action of the ions in the gastrointestinal tract, or by the absorption of the zinc and re-release from immune cells (all granulocytes secrete zinc), or both. Common cold
Weight gain
Zinc deficiency may lead to loss of appetite. The use of zinc in the treatment of anorexia has been advocated since 1979. At least 15 clinical trials have shown that zinc improved weight gain in anorexia. A 1994 trial showed that zinc doubled the rate of body mass increase in the treatment of anorexia nervosa. Deficiency of other nutrients such as tyrosine, tryptophan and thiamine could contribute to this phenomenon of "malnutrition-induced malnutrition".
Urticarial vasculitis (also known as "chronic urticaria as a manifestation of venulitis", "hypocomplementemic urticarial vasculitis syndrome", "hypocomplementemic vasculitis" and "unusual lupus-like syndrome") is a skin condition characterized by fixed urticarial lesions that appear histologically as a vasculitis. : 834

Mechanism
Antibodies are usually raised against foreign proteins, such as those made by a replicating virus or invading bacterium. Virus or bacteria with antibodies opsonized or "stuck" to them highlight them to other cells of the immune system for clearance. Antibodies against self proteins are known as autoantibodies, and are not found in healthy individuals. These autoantibodies can be used to detect certain diseases. C1q
C1q is an integral component within the complement pathway – a complicated cascade of protein interactions, culminating in an immune response against a broad variety of pathogens. The anti-C1q antibodies found in patients with hypocomplementemic urticarial vasculitis activate C1q, which instigates activation of the entire complement pathway. Consequently, levels of all complement proteins become low. Impaired classical complement pathway
The complement pathway is composed of several subset pathways: the lectin/mannose pathway, alternative pathway and the classical pathway.