Let’s face it — pregnancy can cause some pretty weird side effects. Why do you suddenly want pickles dipped in ranch dressing? Why are you crying during a car commercial? And what’s with the daily nosebleeds?

There are also some symptoms no one wants to talk about — like what you see in the toilet. But what about the toilet itself? As in… the seat turning a lovely blue or purple hue?

If you landed on this page, you probably already know the claim that has some pregnancy forums abuzz: Being pregnant can turn your toilet seat blue. Or so the theory goes.

We took a deep dive into this claim so you wouldn’t have to, and here’s what we found.

First off, keep in mind that online reports of the blue or blueish purple toilet seat are coming from both men and women, pregnant and nonpregnant people.

And although the majority of reports of this phenomenon are coming from pregnant people, not all of them are. In fact, it may be affecting people with pregnant and nonpregnant status equally — it’s just that there are more forums (aka opportunities) for pregnant people to talk about it.

We wanted to keep this in mind when considering possible causes.

Those brand new jeans you got yesterday? They could be rubbing off on your skin today.

Blue jeans — especially new ones that haven’t been washed yet — can leave some of their blue dye on your skin, particularly on your rear end since that’s where they tend to be the most form fitting.

Pull them down and sit on the porcelain throne, and you may get up to see that some of the dye has transferred to the seat.

This certainly explains a lot of blue toilet seats — in the bathrooms of men and women. And if you’re pregnant, you may be buying new jeans (or maternity pants in a variety of colors) more often.

Nevertheless, plenty of people experiencing this phenomenon share that they weren’t wearing new jeans at the time, and we believe them. On to the next theory…

Some people have speculated that you may turn the toilet seat blue due to an ingredient in your prenatal vitamin. While this is a tempting theory due to prenatals (often) being a new addition to your routine if you’re pregnant, there are a couple problems with this hypothesis.

Firstly, while prenatal vitamins are specially formulated for the needs of pregnancy — for example, they typically contain more folic acid than standard multivitamins — they really don’t include any specific ingredient that you couldn’t find in other supplements.

And there’s absolutely no scientific support that the contents — even if the vitamins contained blue dye — would turn your backside (and only your backside) blue.

Chromhidrosis is a really rare condition in which you have an excess amount of lipofuscin in your sweat glands. Lipofuscin is essentially pigmented granules that collect in cells throughout the body. With chromhidrosis, the extra lipofuscin in the sweat glands causes you to sweat in color.

Of the many colors of sweat reported with chromhidrosis, blue is one.

Sounds plausible that if you’re secreting blue sweat, you could turn the things you sit on blue — but here are the issues with this hypothesis:

  • We couldn’t find any evidence in the medical literature that chromhidrosis is more common among people who are pregnant.
  • The rarity of the condition makes it seem like an unlikely explanation for the many anecdotal reports of blue toilet seats.
  • In chromhidrosis, the colored sweat is typically located in three places: the face, the armpits, and the breasts. These aren’t exactly body parts that come in contact with the toilet seat.
  • Online community mentions of the blue toilet seat phenomenon don’t generally include stories of blue sheets, clothing, or other staining, which would presumably also occur with chromhidrosis.

Pseudochromhidrosis is just what it sounds like: It’s a condition that mimics chromhidrosis, but it isn’t the same thing. In fact, with pseudochromhidrosis, your sweat is colorless when your body produces it. You don’t have excess lipofuscin turning it any color of the rainbow.

But if you have certain bacteria, fungi, chemicals, or dyes on your skin (or toilet seat), your sweat can react with these and have almost a chemical reaction, causing colored sweat — red, black, blue, you name it. This is a rare, but known, phenomenon.

Some toilet seats may be coated with antimicrobial silver, and some forum authors claim this can cause pseudochromhidrosis when coming in contact with sweat. But this seems like it would be simple enough to test and wouldn’t just affect a person during pregnancy.

Finally, you didn’t think we could bring up any pregnancy side effect without mentioning hormones, did you? Some of the hormones that increase in pregnancy are:

  • progesterone
  • estrogen
  • human chorionic gonadotropin
  • relaxin
  • placental growth factor
  • prolactin
  • human placental lactogen
  • oxytocin

Could these hormones be reacting with your sweat or your skin and turning your toilet blue? After all, we know that “pregnancy glow” is a real skin change that can be traced to hormones and increased blood flow. And like the blue toilet seat, not everyone gets pregnancy glow.

But again, we just don’t have the scientific backing to say for certain one way or the other.

One thing’s for certain: We don’t think the blue toilet seat accounts are made up. So if this has happened to you and you’ve been too embarrassed or weirded out to mention it to anyone, know that you’re not alone.

But for the time being, we don’t have a truly satisfying explanation for why this happens to some people, pregnant or not, who haven’t been wearing new jeans.

And be warned: Healthcare professionals might not believe you if you bring up that this is happening to you. But do so anyway. If enough people report it, it may get a second look and more (well, any) research behind it.