Chrissy Teigen says her swollen lips are due to 'a pesticide or something' on the skin of an orange she bit, not overnight lip fillers

• Chrissy Teigen told fans she had an allergic reaction after biting into an orange.
• The cookbook author guessed "pesticides or something" on the fruit's skin caused her lips to swell.
• But an allergist and immunology specialist told Insider any number of things might've caused it.

Chrissy Teigen is dealing with yet another food mishap.

In a series of Instagram Story videos, Teigen shared that an apparent allergic reaction caused her lips to visibly swell up. Teigen said she thinks the reaction happened because of "a pesticide or something" on the skin of an orange she bit into.

But Dr. Sanjeev Jain, a board-certified allergist and immunologist at Columbia Allergy, told Insider that while Teigen's theory could be right, it's also possible she developed a new-onset allergy to oranges.

Teigen's lip issue started on Saturday

"You're all just gonna think that I got lip fillers, but I didn't get lip fillers between last night and now," the supermodel and cookbook author said on her Stories.

"I, like, bit an orange to try to open it, and I think there must have been like a pesticide or something on it," she continued between bouts of laughter and close-up views of her swollen lips, which she described as being hard and "bouncy" to the touch. She also noted that her nose was a bit swollen too.

Two hours after posting her initial story, Teigen shared another video saying that she thought her lips were getting even bigger instead of smaller. She didn't mention whether she tried taking any over-the-counter medicine to reduce swelling.

On Monday, she shared another photo of her lips, joking that she looked like "a juicy blow-up doll, freshly unpacked."

An expert says this could be a sign of a new-onset allergy to the fruit itself

Dr. Jain, who doesn't know about the model's case specifically and hasn't reviewed any of Teigen's medical history, told Insider that there are a number of possibilities as far as what actually caused Teigen's reaction.

Because we don't know how much time had passed between when she ate the orange and when her lips started to swell, one possibility is that she actually developed a new allergy to oranges.

A delayed response, Jain says, would suggest that her reaction was more likely due to a chemical rather than the allergen in the food itself.

"When people react to food, it's typically the protein component of that food that people have the reaction to," Jain said. "And those reactions generally tend to be quite rapid (within a couple of hours). But reactions to chemicals tend to be delayed (several hours or within 24 hours)."

But this isn't a hard-and-fast rule.

When someone develops a new-onset allergy, Jain said, the reaction could be "delayed and not as severe as it would be if someone kept having reaction after reaction."

The allergy and immunology specialist told Insider that if the swelling started within a couple of hours of when Teigen bit into the citrus fruit, that could signify a food allergy as opposed to a chemical allergy. If it started many hours or even a day later, though, chances are it was a reaction to chemicals.

That said, chemicals don't necessarily mean pesticides.

According to Jain, orange peels contain a class of naturally-occurring chemicals called polyphenols, which he says are known to cause allergic reactions in some people. Our bodies don't distinguish whether the allergen is natural or artificial, he said, so it would be hard to tell without testing whether Teigen reacted to a natural or artificial chemical.

"The part of an allergy specialty that I find most fascinating is that it is a detective job," Jain told Insider.

"We won't [yet] draw the conclusion that it was the orange that did it," he added. "Orange is a suspect, and orange peel is a suspect, and pesticides in orange are a suspect, but we won't jump to that conclusion without investigating."