UKH

Whenever I put sunscreen on, I can taste a bitter, metallic taste in the back of my mouth. This starts within a couple of minutes of applying sunscreen and can last for several hours. I find it quite unpleasant.

I don't think it is getting into my mouth - for example at the weekend I applied a cream sunscreen only to my feet. I washed my hands immediately after, and it still happened. It seems to happen with all brands, and it doesn't make any difference if it is spray/cream/roll-on.

I always assumed that this happened to everyone, but a conversation with colleagues this morning indicated that this is not normal.

Does anyone else experience this? Does anyone know how or why it happens?

There’s a video knocking about with people experiencing a similar effect by applying garlic to their feet. It gets absorbed into the bloodstream and eventually turns up in the mouth. Probably the same with some ingredient of your sunscreen. Random people on the web think the culprit might be oxybenzone. I expect a proper scientist will be along shortly. 

Maybe it is "simply" a synesthesia phenomenon as opposed to the "actually getting into the bloodstream". 

I am a proper scientist, although this is significantly outside my areas of expertise (immunology and protozoan parasites)   

I wonder why this only happens to me and not to other people, though?

I'm not convinced by that. My partner does experience synaesthesia - somewhere I have some drawings he made of what my favourite perfume "looks" like over time as I wear it. This is completely different to anything he experiences, although of course different people may experience synaesthesia in different ways.

The key difference for me, though, is that he can "see" any scent. If that part holds true, I would expect that I would be able to "taste" other things unexpectedly. That doesn't happen to me - it really is only sunscreen. To me, that implies a specific receptor being activated somehow rather than a more general cross-wiring phenomenon.

There’s that weird thing with coriander, which for some is delicious but for others tastes disgustingly like soap; it’s supposedly a genetic thing. Maybe something similar here?

I don't know enough about synesthesia and have no strong opinions in this case or on the phenomenon; I was going to write "mild synesthesia" but that would have suggested greater knowledge than I possess. 
I have at least one similar example for myself (but right now it does not spring to mind - I think it's something that causes me to smell a non existent "burning" smell and like in your case, it's a very specific single stimulus). If this means I have completely misunderstood the entire synesthesia phenomenon, I am fine with that. 

Yes, I know about that one. That's a stereoisomer thing. There are a couple of other examples - for example to some people spearmint and carroway taste identical, but to other people they are very distinct flavours. That happens when two molecules are mirror-images of each other - some people have receptors that can only bind one of the two forms and perceive them as distinct - other people have receptors that can bind both forms and perceive them as the same.

That doesn't explain to me why I can taste it in the first place though!

Psychosomatic? Trauma from a forgotten incident where you actually did taste a load of sunscreen? If this is what it tastes like… 

You know, I'm not planning on deliberately tasting sunscreen to find out...  

Lots of the ingredients get in to your blood [1] and from there in to various exuded and secreted substances including breast milk.  I haven’t seen any study on saliva but I imagine it gets there to.  That would be my best guess.  Even very low concentrations of some things can be sensed strongly by taste.

Many of these absorbed ingredients don’t have enough data to be GRAS which is why I have a bit a disagreement with Jr’s school over their absurdly low threshold for using sunscreen.

You should science this up by looking at ingredients lists of different brands and recording the results.  Little matrix perhaps?

[1] https://jamanetwork.com/journals/jama/fullarticle/2759002

Call yourself a scientist? pfffft! 

In the early days of electricity and battery cells, one chap used an "electrocute my tongue" method to work out the relative conductivity of various liquids  

DMSO ???? 

https://youtu.be/K2M_fQnVqew?si=IBPDYbNOnPluix2R

Oh, yeah - even today I know at least three parasitologists who have deliberately infected themselves with various unpleasant things to see what happens, and probably more who have done it but haven't admitted it.

Personally, I'm not averse to a little electricity on the tongue, but I do stop short of drinking sunscreen, and I wouldn't choose to deliberately give myself malaria either...

No - I have worked with DMSO enough in the lab to know it's not that!

Edited to add that DMSO can indeed penetrate the skin, and is often added to topical medicines applied as creams specifically to aid absorption of the active ingredient. I have worked with it a lot, and had it on my skin, and I've never experienced this - however it may be that presence of DMSO in a sunscreen is aiding absorption of something else that I can test.

Yes, this would be my best guess as to mechanism too. I would need to start tracking ingredients to get more specific than that. I've never used a sunscreen that doesn't do this to me though, so I feel like it would be quite difficult to narrow down.

I'd reccomend you try some of the more unusual suncream formulations such as P20 which is great anyway and very waterproof. 

I have a bottle of P20 right now - I can still taste the taste!

I’ve looked at a few research papers about the genetic variation of people’s ability to perceive bitter stuff. Apparently there’s a very wide variation all the way up to supertasters. There’s not been any mention of anything I recognised as being in sunscreen though. Do you have any weird dislikes of foods that might suggest you’re a supertaster?

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4574037/

Nope! And, in fact I took part in a PROP study during my undergraduate degree, and I am in the category of people who can't taste it at all.

As an impoverished schoolboy I learned to use a 9 volt battery and my tongue to test transistors.  I could tell the polarity of the device (PNP or NPN) and tell whether it was germanium or silicon.

As a weak voltage applied to the tongue has an apparent "taste" that I used to think of as metallic and also from seeing small potential differences between tongue and cheek and fillings with a multimeter years ago I wonder if it is possible somehow that applying sunscreen can result in a tiny change of P.D.  in the body that somehow is interpreted as a metallic taste.

I taste suncream too! I always assumed it was due to being able to smell it and smell and taste being linked. Maybe not though 🤷

Yay, it's not just me!

After a while you might start anticipating the taste, given how you describe it this could trigger the same awful sensations as thinking about licking a 9V battery or with you pick up metal cutlery had it makes that horrible scraping noise.  Just thinking about it has me in discomfort.

What you need is a blinded, randomised test of each ingredient in topical form. I expect sigma sell all the molecules and you can just mix them in doublebase….

Weirdly enough, it's a taste that I do strongly associate with being in the hills!

I feel a grant proposal in the making!

Sometimes when I’m building a really complex mental model of something I’ll fix myself a snack with a really unusual taste, because having that snack again helps bring it all back better than written notes.

This evening’s flavour of note is wild type raspberries that are super ripe and starting to fall off the plant, they have an incredibly strong perfumed flavour well beyond normals raspberries.  I’m hoping to go bilberrying at the weekend, some amazingly verdant plants out there…

You can do the ethics and safety content... I’d anticipate a tightening up of ingredients lists going forwards. Obvs no acute toxicity but without formal tox profiles for them all and the evidence they end up going in to blood….  Also wonder about leachate and the environment for that matter.

Thankfully living in the UK we don’t need to worry much about cumulative effects…

About 40 years ago I got prickly heat from a particular sun cream. A doctor advised to use the ones designed for children or babies, since a lot of the stuff in "adult" ointments is not actually good for the skin. 

Have you tried a strawberry in madras sauce?

I don't get it with suncream, but I get an odd taste in the mouth with certain emollients (moisturisers). I assumed it was some of the ingredients being absorbed through the skin. 

I'm another one! For me it only became noticeable maybe 5 years or so ago ( I'm 60). At 1st I thought it was maybe caused by a specific brand. But my GF used the same brand and didn't experience the effect, and I've had it with other brands since then.

Probably not very helpful but I just have to look at a bottle of sun cream and somehow it is guaranteed to end up in my eyes. Doesn't seem to matter how carefully it's applied or where but I'll invariably have stinging eye balls, tears running down my face. Evil bloody stuff. 

I do seem to be able to refrain from ingesting it though. Like I say, not very helpful :-/ 

I know you said you hadn't experienced that with DMSO but anecdotally I've heard of people having that metallic taste after getting it on them. If you've worked with it I'm sure you know the reason DMSO is dangerous in a lab setting is that not only can it absorb through skin and gloves but can carry other stuff with it. So if it's in your sunscreen it could well be responsible, by bringing some other ingredients along for the ride! As for why others can't taste it I can't say. Taste does seem to be very individual, it could even be an attention thing i.e. other people have a metallic taste but just don't notice it as there tends to be a bit of a sensory overload in situations of applying sunscreen

Are you neurodivergent? Lots of ND people have all kinds of weird sh1t going on with their senses

Yes, I made this point above. However, I checked the ingredients for all three of the sunscreens that I'm actively using at the moment. None of them contain DMSO, and I can taste all of them. So, while I agree that it could contribute to the problem, it's definitely not "necessary and sufficient" to cause it on it's own for me at least.

Do they have oxybenzone in? One Reddit post talking about this phenomenon said DMSO isn't normally in sunscreen but oxybenzone is and does a similar thing.

I wondered the same. Oxybenzone can make its way into the bloodstream https://pubmed.ncbi.nlm.nih.gov/31961417/

Maybe kathrync is unusually good at tasting oxybenzone?

Only one substance has had that effect on me which was a pyrocatchetol based developer (nasty, very toxic stuff). Within a minute of dipping my fingers in it I had such a strong and evil taste in my mouth. Horrible. Needless to say I wore gloves after that. So I'd agree it's most likely a chemical. 

Of the three I currently have on my shelf, one does have oxybenzone. The other two don't. I can taste all three of them.

I bought a couple of different options that don't contain oxybenzone for skiing earlier this year when someone else suggested to me that this could be the cause, but it doesn't make any difference.

Any supplements or medications? Sensitivity to vitamin D, perhaps? Some sunscreens add it and some people don't tolerate normal amounts.

I'd go see a physician anyway. Could be just a harmless allergy or sensitivity to some chemical there, but could be still a more systemic issue (hopefully not!).