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I can totally sense your concern.
The self-tanning lotion contains DHA (dihydroxyacetone). When it is applied to the skin, it stains the outer dead layer of the skin, giving it a tan color. The outer dead layer of skin sheds every four weeks. So, the tan will last for somewhere around that duration. You mentioned that you stopped using it two years back. So, this should have already gone from your skin long ago. Internal cancer (lung cancer) risk from this DHA arises when fumes are inhaled during the application of lotion. This is a chemical. When inhaled, it can trigger cancer process, asthma, and obstructive pulmonary disease, as shown by a few studies. DHA does not penetrate the normal skin beyond the stratum corneum, which is the most superficial layer of skin, also called the dead layer, where it stains. It can reach the blood when it is applied to damaged skin, like any wound. There are hypothetical data regarding this, and not much practical evidence of internal cancer from absorption through the skin. Self-tanning lotions may not have adequate sunscreen in them. So, the risk of sun exposure and sun damage remains the same for people who use tanning lotion and who do not. I mean to say self-tanning lotion does not give you protection against the UV (ultraviolet) rays. It just gives a tan color, which is not a real tan and not protective as a real tan. Sunscreens are to be applied after tanning to protect the skin from UV rays. People think that self-tanning lotions protect against UV rays. I just wanted to clear up that aspect. On the other hand, tanning beds are known to increase the chance of melanoma by 30 %. Tanning sprays are safe in this regard. I feel you should stop worrying about the self-tanning lotion being in your system and causing cancer, as you stopped it two years ago.
Hope this has addressed your concern.