Skip to Accessibility Tools Skip to Content Skip to Footer
What are Nightshades?

What are Nightshades?

I can’t remember the first time someone told me I should avoid nightshades to help my psoriasis, but I can probably guess that my first thought once they explained it was: “not my beloved French fries!” If you hang around the psoriasis communities long enough, nightshades are bound to come up in conversation. You may have been wondering “what’s the deal with nightshades? Does that mean I can’t have pasta sauce anymore? I don’t give two figs about eggplants, but how could I live without pizza?!” Well, here’s a little more info.

What are Nightshades?

Not to be confused with belladonna (deadly nightshade), nightshades are fruits, vegetables, and herbs from a specific family of plants called Solanaceae (okay, so belladonna is part of the same family, but it’s an inedible weed and not relevant to us). The nightshades that people are most familiar with include tomatoes, bell peppers, potatoes, and eggplant. The ones you may not know include tobacco, goji berries, pimentos, and a whole raft of spicy stuff like cayenne, chilia, chili peppers, jalapenos, habaneros, etc. Nightshades do not include black pepper or sweet potatoes.

Why do Nightshades have such a bad reputation?

The short answer? Alkaloids. Alkaloids are toxic molecules produced by lots of different plants, and the Solanaceae family produces a wide variety. Have you ever eaten a potato that was looking a little green and then fallen ill with the worst stomach ache ever? That’s due to solanine, a type of alkaloid potatoes produce to protect themselves from being eaten by insects and animals. The other nightshades produce other types of alkaloids and glycoalkaloids, which are naturally occurring pesticides that prevent them from being eaten. Because ingesting alkaloids can increase irritation and inflammation at high doses, some have suggested that those with autoimmune conditions would be best to avoid them.

Some also take issue with the presence of the lectins and saponins that exist in nightshades. The widely circulated theory is that lectins and saponins create leaky gut, which can worsen autoimmunity (or even create it), but there isn’t a ton of research to support this.

So… are Nightshades bad?

I can feel your eye roll coming, but it really is individualized (don’t shoot the messenger!). Some people are very sensitive to solanine and other alkaloids, and there is anecdotal evidence aplenty to suggest that nightshades really don’t agree with some people. That being said, there is no scientific consensus (that I have found) that suggests we should avoid nightshades. Yes, alkaloids have toxic properties, but the ramifications for a ladybug are much different than for mammals like us. Remember, the key is that they’re only toxic in very high doses. In fact, some alkaloids may actually benefit us. For example, tomatine, found in green tomatoes, may flush out cholesterol. 1 Another, anatabine, is a popular supplement for joint pain.2 And of course, fruits and veggies contain lots of phytonutrients and other great stuff.

To try and balance the scale back a little, I would be remiss if I didn’t highlight one particular survey result. In 2017, a survey on dietary habits was sent to the members of the National Psoriasis Foundation. Of the respondents,52.1% said removing nightshades from their diet had improved their skin. We’ve summarized more of the results here, if you’re interested!

Vicki, I feel ripped off

I know, and I’m very sorry that there is no clear answer. In the spirit of reconciliation, here are a few fun facts that you probably didn’t know:

Fun food facts

  1. Eating habanero peppers was an old remedy for joint pain
  2. An Aussie named Andrew Taylor ate nothing but potatoes for an entire year in 2016
  3. If you feed a bird enough red peppers, the yolk of their eggs will turn red.
  4. Potatoes turn green (produce solanine) when exposed to light as a defense mechanism. The sunlight tells them they’ve been “unearthed” so they ramp up solanine production to prevent from being eaten. That’s why you have to store them in dark places.
  5. Eggplants got their name because early European versions looked like eggs
  6. Caffeine is an alkaloid
  7. Some suspect belladonna was the poison that Shakespeare’s Juliet used to fake her death
  8. Birds are not affected by capsaicin, the chemical that makes peppers hot. Chickens can eat jalapenos like nobody’s business.

Happy munching!


This article represents the opinions, thoughts, and experiences of the author; none of this content has been paid for by any advertiser. The team does not recommend or endorse any products or treatments discussed herein. Learn more about how we maintain editorial integrity here.

  1. Choi K.M., Lee Y.S., Shin D.M., Lee S., Yoo K.S., Lee M.K., Lee J.H., Kim S.Y., Lee Y.M., Hong J.T., Yun Y.P., Yoo H.S., January 2013, Green tomato extract attenuates high-fat-diet-induced obesity through activation of the AMPK pathway in C57BL/6 mice. DOI: 10.1016/j.jnutbio.2012.06.018. Accessed online at
  2. Lanier RK, Gibson KD, Cohen AE, Varga M. Effects of Dietary Supplementation with the Solanaceae Plant Alkaloid Anatabine on Joint Pain and Stiffness: Results from an Internet-Based Survey Study. Clinical Medicine Insights Arthritis and Musculoskeletal Disorders. 2013;6:73-84. doi:10.4137/CMAMD.S13001. Accessed online at


  • kgrace
    4 months ago

    I’ve become fairly certain that eggplant and potatoes cause problems for me but it’s not as obvious that tomatoes and peppers do. So I’m not sure if that makes sense and wonder if I’d actually be better off avoiding all nightshades.
    Tomatoes and peppers are so integral to interesting food (and I can’t eat red meat or eggs or anything corn related —corn starch, corn syrup, dextrose and all the other forms with various names— in addition to the potato ban). Food is definitely a challenge already and going without the tomatoes and chili peppers would be a significant quality of life issue

  • VickiN moderator author
    4 months ago

    @kgrace, oh my gosh, it’s so rare that I meet someone else who is irritated by corn! Corn, gluten, and dairy, are my three biggest triggers. Eggs will do me in as well. I’m totally with you that finding compliant food is a real challenge.
    Thanks for taking the time to comment!
    -Victoria, Community Moderator

  • Poll