The source of your latest allergies could be sitting on your toothbrush.

Twice daily brushing was one of the first hygiene habits you were taught as a child, but popular toothpastes on the market can cause reactions in many who have no idea that the issues they’re experiencing are connected to this routine health ritual.

“The most common signs of toothpaste allergy are mouth swelling, painful canker sores, cracking at the corners of the mouth, the condition known as cheilitis that is marked by dryness, and even gum irritation or an upset stomach,” says New York dentist, Lana Rozenberg, DDS. Red rashes and peeling skin around the mouth are also common, as are lips that turn persistently scaly and itchy.

Simply stopping use of the offending toothpaste will solve most cases, though that can get tricky because numerous formulas on the market contain many of the same ingredients. Even toothpastes marketed as “natural” can cause allergies, say our experts. If you’re experiencing symptoms, it’s essential that you read ingredient labels and look for these most common triggers:

Sodium Laurel Sulfate. “A study from the University of Oslow, Norway showed that canker sores are often precipitated by exposure to the common foaming ingredient, sodium laurel sulfate,” says New York dentist, Gerry Curatola, DDS. Also steer clear of this ingredient’s close cousin, sodium lauryl sulfate. Some brands label their tubes “SLS-Free” to point out that a formula is free of these agents.

Fluoride. The US Food and Drug Administration (FDA) began requiring fluoride warning labels in 1998 because the anti-cavity ingredient is potentially poisonous to small children in large doses. It’s also one of the most common allergy irritants. “A red rash called perioral dermatitis can look like acne, and starts around the lips and may spread to the cheeks, nose or chin as a reaction to fluoride,” says Curatola. 

Flavorings. Here’s where many natural toothpastes can become problematic: Flavors like mint, cinnamon, spearmint, and peppermint can cause burning and rashes. Sticking to a milder ingredient like baking soda is usually safe for most people and is still refreshing, says Joshua Zeichner, MD, Director of Clinical and Cosmetic Research at Mount Sinai Hospital’s Department of Dermatology. 

Preservatives. Propylene Glycol and sodium benzoate are two popular additives that prolong the shelf life of toothpaste and can cause irritation. “If you’re sensitive, buying brands that use fewer ingredients is always a better idea,” says Rozenberg.  

Cutting out the culprit should do the trick, and Rozenberg recommends Benadryl to ease symptoms (if needed) until you’re in the clear. An allergist can also help play detective by patch testing for reactions to these ingredients. And if rashes and redness around your mouth just won’t go away, see your dermatologist—a prescription cortisone cream may be needed to solve the issue, says Zeichner. 


  1. Lana Rozenberg, DDS
  2. Gerry Curatola, DDS
  3. Joshua Zeichner, MD