Does Petrolatum Enhance UV Light?

petroleum jelly

Perhaps a year ago, I read a comment where the author said something along the lines of:

“I wish I wore sunscreen as a youth. I used to just slap on some petrolatum jelly before playing a long afternoon of tennis. Now I have…”

This comment received multiple responses, one of which included something like:

 “I’m so sorry to hear that. And it’s too bad that petrolatum actually worsens the effects of the sun!”

I’ve always thought that this claim was unfounded and ridiculous. But reading that initial comment, I’ve witnessed quite a few people reiterate such a belief. By no means does that provide substantive; rather, it confirms a need to address such a subject.

How Did This Idea Arise?

A magnifying lens requires both convexity and some distance to allow sunlight to physically burn.

A magnifying lens requires both convexity and some distance to allow sunlight to physically burn. This does NOT occur with topical petrolatum application!

While I cannot pinpoint the original explanatory source, proponents claim that this phenomenon occurs because cosmetic-grade petrolatum (white petrolatum) creates a shiny and uniform layer on the surface of the skin, which in-turn focuses and intensifies the UV rays of the sun—similar to how a magnifying lens can channel sunlight into a single beam of (literally) burning heat.

As elegant of an analogy this is, to predicate validity based on such a line of reasoning, would be erroneous. Here’s why:

A magnifying lens uses convexity to compress a given amount of light energy into a relatively smaller quantity of space, whose size is dependent on the convexity of the lens, and the distance between the lens and the “target.” Forced into a smaller quantity of space, this now denser, but still same amount of light energy will naturally increase in strength and potency.

Topical petrolatum obviously does not possess any of these attributes.

Once applied to the skin, the “uniform” layer of petrolatum cannot form and maintain a meaningful degree of convexity, as it hugs the skin’s every contour.

Furthermore, because the strength of the focused beam of light is dependent (to an endpoint distance) on how far the convex (magnifying) lens is in relation to the “target,” the layer of petrolatum would also have to be some distance away from the skin to have any increased strength. So unless you can somehow apply petrolatum without having it touch your skin (imagine a layer of petrolatum in the shape of your face, floating an inch away it), both the distance away and the increase in strength are zero

Let me put it more bluntly: the magnifying glass analogy is a horribly inaccurate representation of the claim that petrolatum enhances UV damage.

But Is This Claim True?

As with any skin care ingredient, let’s look at the research.

Only UVA and UVB rays reach the Earth's surface. Petrolatum mildly "blocks" both.

Only UVA and UVB rays reach the Earth’s surface. Petrolatum mildly “blocks” both.

In a two-part in vivo (single-blind, placebo-controlled) clinical study that tested (in-part) the effects of petrolatum on UVA and UVB absorption, it was shown that petrolatum was able to confer mild blocking effects on both types of UV irradiation.

The two-part study also concluded that petrolatum was more adept at blocking UVB rays compared to UVA rays. This is supported by the fact that, when comparing the average minimal erythema doses (MEDs) achieved from applying a thin (0.1 mL/25 cm2) layer of petrolatum versus a thick (0.3 mL/25 cm2) layer of petrolatum, there was a statistically significant difference between the two groups in terms of UVB light. This distinction was not seen when experimenting with UVA light.

The conclusion that petrolatum actually inhibits a portion of damaging UVA and UVB light, was confirmed by another study, which also demonstrated that both olive oil and glycerin do not (directly) block UVB radiation.

***Note that, when I use the word “block” I am not inferring or explaining how petrolatum protects against UV light. Whether via regenerative absorption like organic sunscreens, scattering like inorganic sunscreens, or another process entirely; that mechanism of action is unknown, though it likely involves some type of degenerative absorption.  

***Also note that, while the study tested both petrolatum and salicylic acid (SA) (a known UV blocker as previously discussed in the Hydroxy Acids Part III: Common Misconceptions post, the study was placebo-controlled for BOTH ingredients, meaning that the mild UV-blocking effects of petrolatum were not inaccurately derived from that of SA.

Petrolatum Protects Against UV Light

Despite the existing canon out there, it turns out that petrolatum actually reduces UV absorption by the skin. Keep in mind that in no way can petrolatum replace a good sunscreen (nor should it). Still, I personally think this conclusion is a gratifyingly ironic sort of repartee to the people who chose to use a certain bombastic analogy… Haha!

So if you should encounter another kook who tells you that Vaseline will cause skin cancer, send them my way! Do any of the daytime products in your routine contain petrolatum? What are you favorites?

Related Posts

  • One of the greatest problems in the U.S. right now is the fact that there is so much misinformation surrounding the health and beauty industry. One great example of this involves the ingredient petrolatum. Many dermatologists consider petrolatum to be one of the best moisturizers (Cosmetic Dermatology, 2002). However, a plethora of misinformation, including erroneous facts…
  • My friend Eric and me! Contrary to popular belief, skin is not just skin. Dermatologists even qualify different skin types on a scale known as the Fitzpatrick scale; different types denote different susceptibilities to skin diseases, treatment plans and options. In a prior interview of mine with African-American dermatologist Dr. Rosemarie Ingleton, M.D., she informed…
  • Thanks largely to the organic and natural product movement, there are a lot of well-intentioned people out there who say things like: Let thy food be thy skin care. If my eighth-grader can't pronounce it, I won't eat it or use it on my face. If I can't eat it, I won't use it on my…

by John Su

10 thoughts on “Does Petrolatum Enhance UV Light?

  1. Sarah says:

    I use Vaseline extensively on my lips. I actually love the slightly greasy feeling. Weird right? I’m sorry to say that I don’t wear anything with a SPF on it except that, and I don’t have any lines or spots on my lips.

  2. Melissa Backus says:

    What an awesome article! (once again!) I have ALWAYS used petroleum jelly of some sort on my lips as it is the only product I’ve tried that doesn’t get chunky, taste weird, cause a reaction, etc. Plus it adds a natural sheen to your lips and you can swipe it over a matte lipstick or stain. I have also always had a problem with my lips getting sunburned but can’t stand the taste of sunscreen in lip balm. I will admit that I thought petroleum jelly might increase sun damage because it is glossy (tanning oil = glossy, tanning oil is supposed to increase your tan) but I am so happy to learn otherwise!

  3. Randy Schueller says:

    Very interesting! I’m a little surprised, though, because I recently read a paper that claimed that mineral oil (and similar materials) are used in the photo-therapy treatment of psoriasis to enhance the effects of UVB treatment. Here’s the reference if you want to check it out:

    Reference: Phototherapy treatment of psoriasis today, Michael Zanolli, MD, Journal of the American Academy of Dermatology Volume 49 • Number 2 • August 2003 http://www.skinderma.com/articles/photo_ps.htm

  4. eastvillagesiren says:

    I use Aquaphor everyday. I swear my lips look plumper, probably because they’re protected from moisture loss. I also use the basic Nivea body lotion (darker blue bottle) and La Roche-Posay Lipikar Balm in the winter. Both contain petrolatum.

    Cheers!

  5. John Su says:

    @Melissa Backus

    Yay! Isn’t debunking myths such fun? And while I know this post put your mind at ease (or at least partially), like I said to Sarah, sunscreen is still necessary.

    I hope to see more of your comments in future posts!

  6. John Su says:

    @Randy Schueller

    While mineral oil is derived from petrolatum, I don’t think they should be treated equally. But let’s look at the research. Ugh, I must sound like one of those obnoxious toddlers that screams the same thing over and over: (Ice cream! Ice cream! Ice cream!) = (Research! Research! Research!) Haha!

    But anyways, I think that you took the facts of the linked article out of context. Here’s why:

    In this 1979 study (http://www.ncbi.nlm.nih.gov/pubmed/507860), multiple emollients were studied to see their effects on UVB transmission. Petrolatum was shown to reduce UVB transmission, while mineral oil had “minimal effects.”

    Then in this 1995 study (http://www.ncbi.nlm.nih.gov/pubmed/7868718), this conclusion was confirmed when testing fewer emollients: “Thick application of petrolatum and emollient creams can reduce transmission of UVB. Mineral oil and a clear liquid emollient did not significantly affect transmission or erythemogenicity of UVB.”

    Finally, in this much more specialized and more in-depth study published in 2005 on mineral oil alone (http://www.ncbi.nlm.nih.gov/pubmed/15888130), it was shown that, “On the vaseline oil pretreated side, significantly more plaques were cleared, especially in severe psoriasis. Scaling and infiltration were significantly improved. Application of vaseline oil was more interesting in thick and scaly psoriasis probably because the oil penetrates the intercellular space allowing an optical matching effect which increases the UV transmission… We strongly recommend vaseline oil pretreatment with UVB TL01 phototherapy in psoriasis, especially in severe psoriasis.”

    Okay, we can definitely confirm that petrolatum does indeed reduce UVB transmission.

    But what about mineral oil?

    Well, the two early studies concluded that mineral oil had minimal or non-significant effects, which most likely means that it did not yield statistically significant figures with a p-test; probably <0.05. The more specialized and more recent study however, found that mineral oil did enhance UVB transmission due to the oil penetrating the intercellular space and allowing an “optical matching effect.” The authors went to conclude that mineral oil would be especially (think yielding statistically significantly results) effective for those with severe psoriasis.

    Now, if you observe those with severe psoriasis, you’ll notice that the plaques are very dry and have tons of flaking skin everywhere. Microscopically, the layers of skin are in disarray: bent, twisted, and misaligned. Therefore, it will reflect UV light in all directions because they’re coming at various and random angles. What mineral oil does is slip between those layers of skin cells (think: INTER-cellular) and normalizes all the weird angles and allow the layers of skin to sit properly on top of each other; to match. It’s kind of like how a zipper will realign all the teeth after a pass. This will therefore, allow the layers of skin to become regular, which will reduce reflection as the UV light can pass through better at a direct angle. Think of how a knife will glance off a bullet-proof vest if it comes in at an angle, but will penetrate if stabbed directly. This is likely the “matching optical effect” that the authors were addressing.

    Also, you have to remember that all of these studies were tested on patients with psoriasis, who have decreased susceptibility to UV transmission. And even in mild to moderate cases, mineral oil had no significant effect. Only those with severe cases did mineral oil produce a significant effect. Basically, the mineral oil induced a change (flat layers of skin) that’s already present in “regular” skin. That significant increase was only a measure of the effects of UVB irradiation when psoriatic skin mimicked normal skin. But as stated above, in normal skin, the layers of skin are already flat, so mineral oil would have no “optical matching effect.”Therefore, this unique finding cannot be applied to the general population.

    Ultimately, it seems logical to conclude that mineral oil does not protect against or enhance UV transmission in “normal” skin.

    Does that all make sense?

    Thanks for taking the time to comment! ;) I can’t wait to write for you guys!

    P.S. Good question. Do you think I should publish this response as a follow up article?

  7. John Su says:

    @eastvillagesiren

    That’s great! Although, if you’re talking about the Aquaphor Lip Repair, that doesn’t actually contain any petrolatum… Lol! Just saying.

    Thanks so much for the continued support!

  8. eastvillagesireen says:

    John,

    Ha ha, you’re right about the Lip Repair ; ) I use it daily, and good ‘ole Aquaphor at night and when I go swimming. It is odd that the Lip Repair doesn’t include petrolatum. Thanks for a very informative, well researched site.

  9. John Su says:

    @eastvillagesireen

    Lol! It is odd that the Lip Repair doesn’t contain petrolatum. But it still reads as a great option for the lips! As always, I appreciate and look forward to your comments.

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>