Tanning under the sun or in a solarium is strongly discouraged. UV radiation breaks down collagen and elastin, and it also damages DNA through oxidative stress (study). Nevertheless, the demand for a bronzed look remains strong. As a result, self-tanners continue to evolve.

The Chemistry of Sunless Tanning
Dihydroxyacetone (DHA) reacts with amino acids in the stratum corneum. This process, known as the Maillard reaction, produces melanoidins that darken the skin surface.
In addition, color depth depends on DHA concentration, skin pH, contact time, and keratinocyte density (review).

Erythrulose as a Complement
erythrulose develops more slowly (24–48 hours). However, when formulators combine it with DHA, it reduces patchiness and creates a more even tone. Consequently, many modern formulas use both sugars to achieve natural results.

Preparation and Application
Hydration reduces DHA’s tanning effect. Therefore, exfoliation one to two days before use is strongly recommended (study).
Furthermore, elbows, knees, and ankles contain thicker stratum corneum. Applying emollients to these areas prevents over-darkening (review).

Vehicles and Formats
Lotions and gels spread evenly and suit beginners well. Meanwhile, foams and sprays absorb quickly and appeal to experienced users who prefer speed.

Formulation Stability
Heat, oxygen, and alkaline pH degrade DHA quickly (review). Therefore, formulators keep products mildly acidic (around pH 3–4) (guidance).
In addition, barrier packaging and minimal headspace improve shelf life. Newer microencapsulation techniques extend stability further.

Safety Profile
The European SCCS confirms DHA is safe up to 10% in self-tanning lotions. Importantly, self-tanners avoid UV-driven collagen and DNA damage (review).
However, the familiar “self-tan smell” results from Maillard by-products. Fragrances can reduce this odor but cannot eliminate it fully (source).

Practical Formulation Tips
• Keep formulas mildly acidic to stabilize DHA (guidance).
• Avoid amine-rich thickeners and proteins that destabilize DHA.
• Use pumps or barrier packs to limit oxygen exposure (review).
• Blend DHA with erythrulose and soothing actives like panthenol or allantoin.
• Explore encapsulation to extend shelf life and reduce odor.

Consumer Guidance
Exfoliate gently before application (study). In addition, apply emollient to elbows, knees, and feet to balance absorption.
Expect DHA to produce visible color within 2–8 hours. Meanwhile, erythrulose deepens the tan gradually over 24–48 hours (clinical study).