What you see: A brown stain on your banana.
What it is: A superficial “burn” from banana sap.
Eat or toss: Eat! As long as the banana otherwise looks fine, it should be good to eat.
Banana latex can stain bananas
When banana bunches are cut off the stem, they often exude a sap. If that sap leaks down the banana it can essentially burn the banana peel, resulting in drippy brown spots, like the ones you see in the image above.
It’s unattractive, but the banana is still perfectly fine to eat.
“The brown is the injured tissue turning brown,” said Jeff Brecht, a professor of postharvest physiology and horticulture at the University of Florida. Chemicals in the sap are “killing cells in the peel and they turn brown.” The damage, fortunately, is restricted to the very surface of the peel. Those injured cells then dry out so it’s not like the banana has an open wound making it more vulnerable to decay.
The staining sap is known as “latex” (though it’s different from rubber tree latex).
“The latex from plants is a caustic material in general,” Brecht said. “It tends to be highly acidic.” Brecht said he’d never heard of cases where banana latex injured a person, “but the peel of the fruit will be sensitive to it.”
Harvesters try to prevent latex stains by quickly placing bananas in tanks of water where the sap can coagulate without touching the peels.
When latex still manages to damage bananas, Brecht said that’s a sign that the water tank wasn’t managed well. They might have waited too long to change the water, or put too many bananas in at once.
Bananas and latex allergies
If you or someone you know has a latex allergy, perhaps learning about this banana sap, often referred to as “latex,” might make you nervous. While it’s true that people with allergies to latex from rubber trees are told to be careful around bananas, my understanding is that this advice is unrelated to the fact that bananas exude this sap.
Rather, bananas are risky for people with latex allergies because bananas produce some proteins that are similar to the allergy-inducing proteins found in latex from rubber trees. So someone with a latex allergy who eats, touches or even smells a banana might have a reaction, but the reaction would likely be to proteins ingested via the banana flesh, not contact with sap exuded from breaks in the banana peel.
People with a latex allergy are typically advised to avoid eating bananas because they could have a reaction. According to the Allergy and Asthma Network, about 30 to 50 percent of people with a latex allergy also have reactions to certain fruits and vegetables. Individual allergies can vary, so proceed with care and check with your doctor if you are concerned.
SOURCES:
- Dr. Jeffrey K. Brecht. Professor of postharvest physiology and horticulture. Horticultural Sciences. University of Florida.
- Postharvest Technology of Horticultural Crops. Edited by Adel A. Kader. 2002. Chapter: 31. Postharvest Handling Systems: Tropical Fruits by Adel A Kader, Noel F. Sommer, and Mary Lu Arpaia.
- Banana Disorders and Diseases. Wageningen University. FreshKnowledge. Accessed May 2025.
- Latex Allergy & Foods. Allergy and Asthma Network.
