How tanning lotion works will vary depending on the type of lotion you are using. Bronzers – which contain dihydroxyacetone (DHA) as their main component – react with the amino acids in the dead layer of skin to produce melanoidins. The melanoidins, in turn, absorb certain wavelengths of light resulting in the browning effect.
Tinglers – which contain Methyl or Benzyl Nicotinate as their main components – increase blood flow on the skin. This exposes the cells responsible for melanin production to more oxygen, resulting in melanin production and hence a darker skin.