Sunscreen for tretinoin users: SPF and timing

People who use tretinoin are told by its labels to wear sunscreen every day, because treated skin can burn more easily. The drug labels say SPF 15 or more, and the American Academy of Dermatology (AAD) recommends SPF 30 or higher for everyone. This guide gives each figure with its source, explains which sunscreen the sources describe, and covers sunburn, summer and trips. For what the drug is and what it treats, see the tretinoin guide.

Skinli gives general education and is not a doctor. Tretinoin is a prescription drug in the US, and your prescriber picks the strength and the schedule and decides when to pause it. The generic tretinoin leaflet tells patients to ask their physician which SPF level they need, so ask at your next visit.

Why tretinoin labels ask for sunscreen

Each label below is published on DailyMed, the National Library of Medicine's database of drug labels. They agree that tretinoin raises the skin's reaction to sunlight.

• The generic tretinoin cream leaflet says: "Therapy with tretinoin may make your skin more susceptible to sunburn and other adverse effects of the sun".
• The Retin-A Micro gel label says the gel "can cause photosensitivity." Photosensitivity means the skin reacts more strongly to sunlight.
• The Renova cream label asks patients to avoid or minimize sunlight "because of heightened sunburn susceptibility."
• NICE, the guideline body in England, lists photosensitivity among the effects of tretinoin combined with the antibiotic clindamycin.

One label gives a count. In the trials on the Atralin gel label, sunburn was reported by 7 of the 674 people on the gel and by 3 of the 487 people on a gel with no drug. That is 1 percent of each group.

One report found the opposite. In 2009 the journal Photodermatology, Photoimmunology and Photomedicine published four small trials of a new 0.05 percent tretinoin gel in healthy volunteers. Two trials with 51 people in total tested for a direct light reaction, and two with 72 people tested for a light allergy. The report states: "No phototoxic or photoallergic reactions occurred". Its first author worked at the company developing that gel, and the report itself says that "current US drug labeling" describes tretinoin as a phototoxin, a substance that harms skin when light falls on it. The labels still carry their warnings, and this guide follows the labels.

The generic label also describes studies in mice exposed to strong ultraviolet lamps, and says that although their meaning for people "is not clear, patients should minimize exposure to sunlight or artificial ultraviolet irradiation sources." The tretinoin side effects guide reports those studies in full.

What SPF each source gives

SPF stands for sun protection factor, the number printed on a sunscreen.

Source	What it says
Generic tretinoin cream leaflet	"An effective sunscreen should be used any time you are outside". Ask your physician for an SPF level
Retin-A Micro gel leaflet	"use a sunscreen with sun protection factor (SPF) of 15 or more."
Renova cream label, for fine wrinkles	"sunscreens (minimum SPF of 15) and protective clothing"
Altreno lotion leaflet	SPF "of 15 or more", protective clothing and a wide-brimmed hat
Atralin gel label	"sunscreen of at least SPF 15 and protective clothing"
Ziana gel label (tretinoin with clindamycin)	"A sunscreen should be applied every morning and reapplied over the course of the day as needed." No number is given
Tri-Luma cream label (tretinoin with two other drugs, for melasma)	"During the day, use a sunscreen of SPF 30, and wear protective clothing."
AAD, sunscreen questions page	"broad-spectrum (UVA and UVB) protection, has an SPF of 30 or higher, and is water resistant."
FDA, sunscreen page	"broad spectrum sunscreens with sun protection factor (SPF) values of 15 or higher"

The lowest figure on the labels is SPF 15. The AAD asks for SPF 30 or higher, and so does the one tretinoin label written for melasma, a condition of dark patches that sunlight makes worse. Skinli's own plan asks for SPF 30 every morning, which meets both figures.

Which sunscreen the sources describe

The sources describe features of a sunscreen. None of them tested one sunscreen against another in people using tretinoin, and none names a product.

• Broad-spectrum. The term means the sunscreen protects against both UVA and UVB, two kinds of ultraviolet light. The AAD and the FDA both ask for it.
• Water resistant. This is on the AAD's list. The AAD adds that no sunscreen is waterproof, so it has to go on again after swimming or sweating.
• Mineral sunscreen for sensitive skin. The AAD's retinoid page says: "If you have sensitive skin, look for a physical sunscreen containing the ingredients titanium dioxide and/or zinc oxide." Its sunscreen page says dermatologists recommend these sunscreens, also called mineral sunscreens, for people with sensitive skin. The guide to mineral vs chemical sunscreen explains the two kinds.
• A base that suits acne. NICE advises people with acne who use sunscreens "to avoid oil-based and comedogenic preparations." Comedogenic means likely to clog pores. The generic tretinoin leaflet uses the opposite word, noncomedogenic, for the morning moisturizer with sunscreen.
• Low in alcohol. The tretinoin label asks for caution with "products with high concentrations of alcohol". The label does not mention sunscreens by name, so read this as a general caution that also covers them.

The AAD also says: "The best type of sunscreen is the one you will use again and again." For more on choosing one, see how to choose a sunscreen for your face and sunscreen for acne-prone skin.

One practical check comes from the FDA: a sunscreen with no expiration date on it "should be considered expired three years after purchase."

How to use sunscreen on tretinoin days

Tretinoin goes on at bedtime and sunscreen goes on in the morning, so the two are never layered.

1. Morning wash. Wash with a mild cleanser and pat the skin dry.
2. Moisturizer and sunscreen. The generic leaflet recommends "a moisturizer or a moisturizer with sunscreen" every morning after washing. The AAD's routine page gives the same last step: "Apply moisturizer and/or sunscreen." The moisturizer with tretinoin guide covers the moisturizer.
3. Timing. The AAD says: "Apply sunscreen to dry skin 15 minutes before going outdoors."
4. Reapply. The FDA says: "Reapply sunscreen at least every two hours, and more often if you're sweating or swimming." The AAD says a moisturizer or makeup with SPF needs the same reapplying outdoors.
5. Clothing. The labels pair sunscreen with clothing. The Altreno leaflet asks for "a wide-brimmed hat to cover the treated areas." The FDA suggests limiting time in the sun "between the hours of 10 a.m. and 2 p.m., when the sun's rays are most intense."

Protection is also asked for on cloudy days and indoor days. The Retin-A Micro label asks for protection "even on days when it is not sunny or inside activities are expected." The Ziana leaflet says to use sunscreen on treated skin "even on cloudy days".

The labels also tell patients to stay away from sunlamps and tanning beds. The Retin-A Micro leaflet says: "You should avoid sunlamps, tanning beds, and ultraviolet light during treatment".

What sunlight does to tretinoin itself

Light breaks the drug down, which is one reason the labels direct evening use.

Laboratory study	What it found
International Journal of Pharmaceutics, 2008	Light made to copy sunlight broke tretinoin down. "The UVA component", one type of ultraviolet light, "is the major contributor"
Cutis, 2006, written by Johnson & Johnson staff	After 2 and 6 hours of simulated sunlight, 19 percent and 10 percent of the tretinoin in a 0.025 percent gel remained unchanged. In a 0.1 percent microsphere gel, which carries the drug in tiny spheres, 94 percent and 84 percent remained

These were tests on the products, with no patients. The authors of the Cutis study wrote that simulated sunlight "is not entirely reflective of actual conditions". The authors of the 2008 study suggest that the breakdown of tretinoin "may contribute to the photosensitivity" seen during treatment. How to use tretinoin covers the night schedule.

Sunburn, summer and trips

Sunburn. The labels agree. The generic leaflet says: "If you do become sunburned, stop your therapy with tretinoin until your skin has recovered." The Atralin leaflet says to stop "until your skin has healed and is back to normal." The Renova label says the cream is not for a patient who "is sunburned".

Summer. None of the labels read for this guide tells patients to stop for a season. The generic label says people "required to have considerable sun exposure due to occupation and those with inherent sensitivity to the sun should exercise particular caution."

A beach trip. No source gives a number of days to stop before travel. Tell your prescriber about the trip and ask whether to pause.

Tanning. Questions about whether tretinoin fades a tan or stops one have no answer in the sources read for this guide.

Other medicines. The Renova label names five groups of drugs that raise sun sensitivity: "thiazides, tetracyclines, fluoroquinolones, phenothiazines, sulfonamides". Tetracyclines include antibiotics that are prescribed for acne, and NICE says they "can cause photosensitivity". Tell your prescriber about every medicine you take.

Acids and dark patches. The FDA says alpha hydroxy acids, such as glycolic acid, increase the skin's sensitivity to ultraviolet light. See salicylic acid with tretinoin. For melasma, the Tri-Luma leaflet says it "can get worse with even a small amount of sunlight." See hydroquinone and tretinoin.

When to contact your prescriber

Stop tretinoin and contact your prescriber after a sunburn on treated skin, and ask when to start again. Do the same if the skin blisters, crusts or swells, which the label lists among reactions in sensitive people. Mention any job, sport or trip that keeps you outdoors for hours, because the label asks for particular caution in that case. If a burn on treated skin is not healing, see a doctor in person.