Claim: Is Self-Tanner Safe, and Should You Be Wearing It Overnight?

Question

Many people avoid going into the sun to tan due to health risk factors like skin cancer and sun spots. But is fake tanning healthier than going into the sun? Fake tanning involves a chemical process using dihydroxyacetone (DHA) which binds with the amino acids on the top layer of the skin to produce melanoidins. This article claims that it is the same chemicals that turn fruits brown when they go bad. The author believes that most products on the shelf are safe and don’t have any pronounced aging effects because the chemical only interacts with the top layer of skin which is composed of dead skin cells. She says the main cause of aging is free radicals interacting with collagen and elastin and doesn’t have any correlation to fake tanning in terms of speeding up aging. However, in another article, the author says she went to a dermatologist who spent hours removing little “brown-heads” that clogged her pores due to fake tan damaging the sebum and dead skin. Dr. Francesca Fusco, Assistant Clinical Professor of Dermatology at Mount Sinai in New York explains how the DHA not only stains the pores but causes those free radicals to interact with molecules called Amadori products causing oxidation. This oxidation happens two times quicker than naturally occurring UV-generated free radicals and causes dark spots and oxidative stress which results in aging effects. They recommend combining fake tan with rich anti-oxidant moisturizer to reduce these effects. 

Answer 1

There isn’t typically a concern with leaving self tanner on overnight, considering that it is a leave-on product and is designed to sit on your skin for long periods of time. Self-tanner is much safer than tanning beds or direct sun exposure because they do not expose your skin to harmful UV radiation, which is the main cause of skin cancer, premature aging, and sun damage to your skin. Self tanners use ingredients like DHA or erythrulose that react with amino acids on the skin’s surface to create a temporary “fake” tan. These ingredients can create something called “free radicals”, which are unstable molecules that form when your body is exposed to sunlight or certain chemicals. When they become unstable, it causes oxidative stress, which can damage your skin’s collagen and elastin, which can lead to wrinkles, sagging and premature aging. Self tanner still can create some free radicals, but they are mostly in the outer, dead layers of skin, making them much less harmful than the UV damage caused by tanning beds or real sun. The bigger concern to your body is inhaling spray tans, which can cause cell damage or asthma over time, so wearing a mask when you get a spray tan is highly recommended. 

https://www.consumerreports.org/health/is-self-tanner-safe-a3329623598/

https://evolutiondermatology.com/are-self-tanners-ever-safe/

Answer 2

Think of this as your investigation log. Answer each question to explain what you discovered and how you got there.

1. Write a brief overall summary of your findings.

Yerba mate does contain caffeine and can boost energy, so that part of the claim is accurate. Moderate consumption appears safe for most adults. However, the claim about cancer risk is more nuanced—evidence suggests the risk is mainly linked to long-term heavy consumption and drinking it very hot, rather than occasional use.

2. What primary sources did you find (e.g., transcripts, videos of politician speeches, tweets from public figures, scientific studies)? For each source, write at least one or two sentences explaining what you learned. Include all links.

International Agency for Research on Cancer
Link: https://www.iarc.who.int/wp-content/uploads/2018/07/pr244_E.pdf
IARC found that drinking very hot beverages (including yerba mate) above 65°C (149°F) is “probably carcinogenic.” This suggests the temperature of the drink, not just yerba mate itself, plays a major role in cancer risk.

• Memorial Sloan Kettering Cancer Center herbal database 
• Link: https://www.mskcc.org/cancer-care/integrative-medicine/herbs/mate
  This source explains that yerba mate contains caffeine and can cause side effects like insomnia, anxiety, and a fast heart rate. It also notes possible interactions with medications.

3. What secondary sources did you find (e.g., newspapers, magazines)? Only use secondary sources if sufficient primary sources are not available. For each source, write at least one or two sentences explaining what you learned. Include all links.

Mayo Clinic
Link: https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/expert-answers/yerba-mate/faq-20058343
Mayo Clinic summarizes research showing moderate yerba mate use is generally safe but links long-term heavy use (1–2 liters daily) to higher cancer risk.
4. What potential biases or interests might each of your sources have?

• IARC (WHO): Focuses on identifying cancer risks globally. It may emphasize caution when evidence suggests possible harm.
• Memorial Sloan Kettering: A cancer-focused institution, so it may highlight risks and interactions more strongly.
• Mayo Clinic: A general medical source aimed at public health education; tends to present balanced, cautious summaries.

5. What evidence supports the claim you are fact-checking?

• Yerba mate contains caffeine, which increases alertness and energy (confirmed by Mayo Clinic and Sloan Kettering).
• Studies reviewed by Mayo Clinic show a link between heavy, long-term consumption and increased risk of certain cancers.
• IARC classifies very hot beverages (including mate) as “probably carcinogenic.”

6. What evidence undermines the claim you are fact-checking? 

• Moderate consumption is not strongly linked to health problems for most adults.
• Cancer risk appears tied more to temperature and quantity than to yerba mate itself.
• Some research suggests potential benefits (like effects on cholesterol and inflammation), though more studies are needed. 

7. What happened when you tried contacting the person or group who made the original claim? (Always try to contact them—it’s okay if you don’t get a reply. For example, if the claim is that the president said something, try reaching out to the administration. If it was a Bluesky user, message that user on Bluesky.)

I attempted to locate and contact the original source of the claim, but no direct contact information was available. I was unable to get a response before completing this fact-check.

Answer 3

What I have gathered from my research is that self-tanner with DHA is generally considered safe for external use. DHA is the only FDA-approved tanning ingredient, according to talkingtan.com. DHA only reacts with the dead layer of our skin, meaning it sits on the outside and doesn't seep in. Obviously, everyone's skin is different, so some people might have reactions to the ingredients, while others may not. One thing to note is that spray tans pose inhalation risks, as DHA is not approved for the inside of our bodies.

The part of the claim that states DHA causes free-radical formation or oxidative stress is supported by the evidence I found as well. Talkingtan.com states that under UV exposure, DHA-treated skin can produce up to 180% more free radicals than untreated skin. However, the part of the claim that states DHA "doesn't speed up aging" isn't totally accurate, as oxidative stress can be directly linked to aging processes.

Overall, this claim is mostly correct, as it states DHA is only approved for external use, which is true. I also found that DHA only reacts with dead skin cells, so the chemical won't affect any other part of our skin. Lastly, it is safer than UV tanning. However, I did learn that DHA does generate free radicals, and the evidence I found does not support the claim that DHA has "no aging effects".

https://talkingtan.com/dihydroxyacetone-dha-skin-care-and-tanning

https://www.healthline.com/health/is-self-tanner-bad-for-you