Same as ADH1A and ADH1B, however, the enzyme is inefficient in ethanol oxidation, but it is the most active as a retinol dehydrogenase, thus it may participate in the synthesis of retinoic acid, a hormone important for cellular differentiation. A single nucleotide polymorphism ADH7 is associated with the risk of squamous cell carcinoma of the head and neck (Wei et al., 2010). Here, ADH7 is linked to squamous cell carcinoma.