Zinc Oxide and Calendula Oil: Can You Make Your Own SPF?

We are not going to give you a calendula oil and zinc oxide sunscreen recipe, because nothing we could cite would let you know what SPF you had made. Zinc oxide is a real sunscreen ingredient, but the number on a sunscreen bottle comes from standardized testing that a kitchen cannot reproduce, and calendula oil is not a sunscreen. What follows is what the sources do say, where calendula oil fits around sun exposure, and what to do instead.

Calendula oil bottle

Calendula Oil

Our own small-batch calendula oil, in sizes from 0.5 oz to bulk.

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What a sourced recipe would have to contain, and why one does not exist

A usable sunscreen recipe needs four numbers: how much zinc oxide, how evenly it is dispersed, how thick a layer is applied, and the resulting SPF. We found a source for only the first, and only as a regulatory ceiling. The text of 21 CFR 352.10 on the eCFR lists "zinc oxide up to 25 percent" as a permitted sunscreen active (eCFR, 21 CFR 352.10; we read the text but did not verify its current enforcement status). A ceiling is not a recipe. It says nothing about how much of the 25% survives mixing into an oil, how it settles, or what protection a given blend delivers.

The other three numbers do not exist outside a lab. FDA explains that sunscreens are tested to find "the amount of ultraviolet (UV) radiation exposure it takes to cause sunburn" with and without the product, and SPF is based on that comparison (FDA, Sunscreen: How to Help Protect Your Skin from the Sun). FDA regulates sunscreens as nonprescription drugs, and in its guidance on cosmetics notes that "sunscreens are a case in point" of a product regulated as a drug in the US (FDA, Cosmetics & U.S. Law). Our reasoning from those two pages is that a home blend could not legitimately carry an SPF claim, though FDA has no page on homemade sunscreen specifically that we found.

What happens to homemade sunscreen recipes in practice

A 2019 study in Health Communication examined sunscreen recipes on Pinterest. Of the pins analyzed, 95% presented homemade sunscreen as effective, and 68% recommended recipes that would give insufficient UV protection; about a third made SPF claims, ranging from SPF 2 to SPF 50 (Nationwide Children's Hospital summary of Merten et al., 2019). It was an analysis of pins, not lab SPF testing, so the 68% is a judgement of the recipes, not a measurement. The study's authors advised FDA-regulated broad-spectrum SPF 30 or higher sunscreen. That matches the American Academy of Dermatology, which recommends broad-spectrum, water-resistant sunscreen of SPF 30 or higher, reapplied about every two hours or after swimming or sweating (AAD, sunscreen recommendations).

Our own position follows from that: the calendula part of the recipe adds no protection you can count on. Published SPF numbers for calendula exist, but they are laboratory spectrophotometer estimates for distilled essential oil, not infused oil: an in vitro SPF of 8.36 for the essential oil in a 2019 study (Lohani et al., J Cosmet Dermatol, 2019) and about 14.8 for a cream containing it in 2012 (Mishra et al., J Young Pharm, 2012). Neither involved human skin or a petal-infused oil like ours, and neither is a basis for relying on a bottle of calendula oil in the sun. We have not measured an SPF for our own oil and do not state one. Our SPF page goes through this in more detail.

Where calendula and zinc oxide do already meet

The two ingredients appear together in baby and barrier products, and the way they are used there is instructive. Weleda's calendula diaper cream lists water, sweet almond oil, sesame seed oil, zinc oxide, beeswax and lanolin ahead of calendula flower extract, and states "12% Zinc Oxide" (Weleda US product page, read 2026). A mainstream baby ointment lists zinc oxide at 40% as the active ingredient, with calendula flower extract as one of many minor inactive ingredients (Burt's Bees Baby product page, read 2026). We have not tested either product. Reasoning from the ingredient lists, in these formulas zinc oxide is the functional ingredient and calendula is a supporting one, and they are made with preservation systems and manufacturing controls that a kitchen blend lacks. A water-containing product needs preservation (Halla et al., Molecules, 2018), which is one more reason a home-made lotion version is a bigger project than stirring powder into oil. See our diaper cream page for that product category.

A decision path for sun days

  1. Need protection before going out? Use a commercially made, broad-spectrum SPF 30 or higher sunscreen. Zinc oxide products are on the shelf already; choose one whose label gives the SPF and the active ingredient percentage. This is the step no oil can replace.
  2. Infant under six months? FDA says sunscreen is not recommended for infants under six months and to ask a doctor. Ask your pediatrician about shade, clothing and timing. Do not improvise a mix.
  3. Skin already red or sore from sun? That is a sunburn question. A severe sunburn is a matter for a doctor, not a recipe. Calendula oil is not a sunscreen and not a substitute for medical care; our sunburn page sets out what the evidence does and does not say about it.
  4. Using calendula oil on skin that is also getting sun? It does not replace sunscreen, and we make no claim that it protects skin from UV.

If you still want to formulate

If you make cosmetics and want a calendula-containing product for sun-exposed skin, the honest lane is a non-SPF product, such as a post-sun body oil or a spray (see our after-sun spray page), labelled and described without any protection claim. FDA looks at "intended use," which claims and reputation can establish, when deciding whether something is a cosmetic or a drug (FDA, Is It a Cosmetic, a Drug, or Both?). A product described as sunscreen is a drug in the US, which is a different regulatory category. For that, you need a licensed cosmetic chemist or a regulatory adviser, not a blog recipe.

If you do want an oil for your own formulations, we make a calendula oil in sizes from 0.5 oz up, with batch documentation on request. We offer it as an oil-phase ingredient, not as sun protection.

Calendula oil bottle

Calendula Oil

Nature's Golden Botanical, bottled: small-batch calendula oil in sizes from 0.5 oz to bulk.

From $13.99

Shop Calendula Oil →

Sources & Further Reading