What Are Nightshade Allergies?

Nightshades are foods in a family of flowering plants that go by the Latin name Solanaceae. The family includes some types of trees, vines, herbs, and crops. Many nightshade plants are popular foods in most cultures, including tomatoes, potatoes, and peppers. But they also contain high levels of substances called alkaloids that may cause health problems.

It's not common, but some people have an allergy or sensitivity to nightshades. There is also some concern that these vegetables may contribute to inflammatory conditions, like arthritis.

This article discusses the health impacts of nightshade foods and how to determine if you have an allergy.

Close-up of female hands with bunch of carrots and fresh organic vegetables in a wicker basket.

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Nightshade Allergy Causes

Most of the concern about nightshades appears to focus on a substance called alkaloids.

Alkaloids are a type of phytochemical, which is a naturally occurring compound produced by plants, especially plants in the nightshade family. This compound has long been studied because of its effects on the body and potential uses for medications, drugs, and poison.

Plants produce alkaloids to protect themselves from mold, disease, and pests. The common types of alkaloids found in plants are:

  • Solanine
  • Nicotine
  • Capsaicin

Most people experience no negative health effects after eating nightshades because the alkaloids are eaten in small amounts relative to body size.

However, the concentration of alkaloids is higher in the stems, leaves, and unripe vegetables. Some research claims eating a large number of green potatoes or potato tops may lead to toxicity.

While uncommon, some people may experience sensitivities or allergies to the alkaloids in nightshades. A food sensitivity is a chemical reaction to a food and doesn’t involve an immune response, while an allergic reaction is triggered by your immune system, which falsely detects a harmless food as something harmful.

In addition, some people may experience an allergy to the fruit or vegetable itself instead of the alkaloid.

Common Edible Nightshades

While some nightshade plants may contain higher amounts of alkaloids, they also contain other vitamins and minerals important for your overall health and well-being. For example, tomatoes contain the compound lycopene, which may help lower heart disease and cancer risk.

Here are some of the most popular nightshade fruits, vegetables, and spices:

  • Tomatoes
  • Potatoes
  • Hot peppers
  • Bell peppers
  • Eggplant
  • Goji berries
  • Blueberries
  • Tomatillos
  • Cayenne pepper
  • Chili pepper flakes
  • Chili powder
  • Paprika

Symptoms of a Nightshade Allergy

People with an allergy to nightshades may experience symptoms after eating a food from the nightshade family, like:

  • Skin rash or hives
  • Itchiness
  • Nausea and vomiting
  • Increased mucus production
  • Sore muscles or joints
  • Swelling of the face or throat
  • Inflammation

An allergy is different from a food sensitivity or intolerance. Symptoms of an allergy occur when your immune system reacts to a harmless substance, such as a food. On the other hand, sensitivities and intolerances cause a chemical reaction in your body when you eat a certain food. Symptoms are not caused by an immune system response.

Sensitivity and intolerance symptoms tend to be less severe than an allergy. The symptoms primarily affect the digestive system. A nightshade intolerance may cause symptoms such as:

  • Heartburn
  • Bloating and gas
  • Nausea and vomiting
  • Diarrhea

Effects of Nightshade on Autoimmune Diseases

Despite the health claims that nightshades increase inflammation and may aggravate an autoimmune disease (a condition in which the immune system mistakenly attacks the body), the research is still limited to support these claims.

One autoimmune condition that has been researched reagarding nightshades is inflammatory bowel disease (IBD). IBD is a pair of conditions (Crohn's disease and ulcerative colitis) characterized by inflammation in the digestive system, particularly the small and large intestines.

A mouse study suggested nightshade vegetables may increase intestinal inflammation and worsen IBD symptoms. One drawback to this study is that researchers used a larger proportion of alkaloids in the mice than the average person would take in from food. So, it’s unclear if smaller doses cause the same increase in inflammation.

Some research suggests that increases in intestinal inflammation increase the likelihood for autoimmune diseases to develop. So, if nightshade vegetables do increase inflammation, they may raise the risk for autoimmune diseases such as rheumatoid arthritis, celiac disease, and Hashimoto’s disease.

While there isn’t enough research to determine if nightshade compounds cause or worsen autoimmune diseases, if you are concerned, you may wish to consider reducing them to see if this decreases your symptoms.

Nightshades are listed as foods to avoid in the Autoimmune Protocol Diet because they may worsen symptoms. This diet is a modification of the Paleolithic diet (focusing on whole foods and non-processed meats) and begins with the elimination of specific foods. However, the effect isn’t scientifically proven.

Diagnosis of Nightshade Allergies

With any food allergy, you’ll want to start keeping a journal to track any patterns you notice among your diet, your lifestyle, and your symptoms. Nightshade allergies are rare, so you’ll also want to look at more common allergens, like dairy, nuts, seafood, soy, and gluten.

Your healthcare professional may recommend allergy tests to help diagnose a specific allergy, such as:

  • Skin-prick test: During this test, your healthcare provider pricks your skin with suspected allergens and monitors for a reaction.
  • Blood test: During this test, a sample of your blood is taken to test for allergy-related antibodies to specific foods.

Treatment for Nightshade Allergies

The typical treatment plan for food allergies involves avoiding foods containing the allergen. Your healthcare professional may ask you to keep a food journal to monitor your symptoms and any potential symptom triggers.

The treatment plan may also include medications to counter allergic reactions when exposed. Common medications that may be prescribed include:

  • Antihistamines: These block the action of histamine, which is released in an allergic reaction and produces symptoms such as hives and sneezing. Examples are Zyrtec (cetirizine), Allegra (fexofenadine), and Clarinex (desloratadine)
  • Decongestants: These help constrict blood vessels so mucus can drain. Examples include Sudafed (pseudoephedrine), Sudafed PE (phenylephrine), and Afrin nasal spray (oxymetazoline).
  • Anticholinergic nasal sprays: These dry up nasal secretions. An example is Atrovent Nasal (ipratropium)
  • Steroid nasal sprays: These decrease inflammation and take a few days to provide relief. Examples are Flonase Allergy Relief (fluticasone propionate) and Nasonex (mometasone).
  • EpiPens (epinephrine injection): This injection is used to stop a severe whole-body allergic reaction called anaphylaxis, which can be life-threatening.

Food Substitutions for Nightshade

Substituting other foods for nightshades can be simple when you know the right fruits and vegetables to use. Here are some easy swaps for popular nightshade foods:

  • Instead of tomato sauce, use olive oil, pesto, and Alfredo sauce.
  • Replace blueberries and goji berries with raspberries, strawberries, cranberries, or cherries.
  • Instead of eggplant, use shitake or portabella mushrooms.
  • Instead of bell peppers, use radishes, carrots, Swiss chard, onion, or celery.
  • Replace white potatoes with sweet potatoes, squash, radishes, cauliflower, turnips, or parsnips.
  • Instead of paprika, cayenne, chili powder, or red pepper flakes, add black pepper, white pepper, cumin, basil, oregano, turmeric, or parsley.

Summary

A nightshade allergy is an immune response to the compound in nightshade plants called alkaloids. Types of nightshade plants include potatoes, tomatoes, peppers, red pepper flakes, eggplant, and paprika.

Symptoms of a nightshade allergy include congestion, skin rash, itching, redness, and digestive problems. Food allergies are diagnosed with a skin prick test or blood allergy test. They are treated by avoiding the allergen and medications to reduce the immune response.

A Word From Verywell

A nightshade allergy isn't common. Still, people who are sensitive to it could experience bothersome symptoms and increased inflammation. If you are sensitive to nightshade foods, there are options for substituting these foods. Talk with your healthcare professional if you believe you have a food allergy. They can help determine if you do have an allergy and which foods to avoid.

Frequently Asked Questions

  • Are nightshades bad for you?

    No, nightshades aren’t necessarily bad for you. Some people with
    allergies, intolerances, or autoimmune diseases may experience adverse reactions when eating nightshades, but there is limited research to support these effects.

  • Which nightshades have the most alkaloids?

    Alkaloids are most concentrated in nightshades like potatoes, tomatoes, and eggplant.

  • What are the health benefits of nightshades?

    Many nightshade vegetables are high in vitamins, minerals, fiber, and antioxidants beneficial to health. For example, tomatoes contain lycopene, which helps protect against heart disease and cancer.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Imran M, Ghorat F, Ul-Haq I, et al. Lycopene as a natural antioxidant used to prevent human health disorders. Antioxidants (Basel). 2020;9(8):706. doi:10.3390/antiox9080706

  3. Li S, Wang T, Xu B, Indukuri V, Vanamala J, Reddivari L. Anthocyanin-containing purple potatoes ameliorate dss-induced colitis in mice. Current Developments in Nutrition. 2020;4(Supplement_2):426-426. doi:10.1093/cdn/nzaa045_059

  4. Fasano A. Leaky gut and autoimmune diseases. Clin Rev Allergy Immunol. 2012;42(1):71-78. doi:10.1007/s12016-011-8291-x

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By Ashley Braun, MPH, RD
Ashley Braun, MPH, RD, is a registered dietitian and public health professional with over 5 years of experience educating people on health related topics using evidence-based information. Her experience includes educating on a wide range of conditions including diabetes, heart disease, HIV, neurological conditions, and more.