Trying Pistachio OIT First May Ease Cashew Desensitization

First undergoing oral immunotherapy (OIT) for pistachio may ease cashew OIT in those with allergies to both, a new study finds.

These are findings from a Mount Sinai Icahn School of Medicine study that included five children severely allergic to cashew, who also had a pistachio allergy. Cashew and pistachio are often cross-reactive, meaning the allergies can go hand-in-hand because of similarities in each nut’s proteins.

Cashew is known to be a particularly potent allergen. The five patients tried to do cashew OIT but reacted even to the low, starting dose in the office. Their symptoms, which included abdominal pain, swelling, vomiting, coughing and wheezing, were treated with antihistamines, epinephrine, or a combination.

So the Mount Sinai team changed tactics. They brought the patients back in, and instead started them on pistachio OIT.

In OIT, patients start by eating a small amount of their food in a daily dose. Over several months, they gradually increase the amount consumed.

The starting pistachio dose ranged from 10 to 15 milligrams (mg), which all five tolerated. One of the patients opted to stop at this point, due to symptoms related to pistachio dosing at home.

After reaching their highest pistachio dose, which ranged from 200 mg to 1,000 mg, the four remaining patients began cashew OIT. On the second try, they all tolerated the starting low doses of cashew either at the same or a higher level as they previously reacted to. They were also able to continue on and reach maintenance for cashew.

Three reached a dose of 1,000 mg of cashew, while one reached 900 mg. One cashew is about 300 mg, while one pistachio is about 150 mg. Patients ranged in age from 4 to 17.

Cashew Allergy Often Potent

“We know that cashew oral immunotherapy will help desensitization to pistachio, but it hasn’t been shown to go the other way,” says lead study author Dr. Dana Greene, a Mount Sinai allergy-immunology fellow. “Because they are so cross-reactive, we think that starting with pistachio helped some of that desensitization to cashew.”

Cashew tends to “be the more potent of the two,” she notes. Potency doesn’t refer to the severity of reactions, which can be equally severe in both. “Potentially for patients who have really high levels for cashew, we can start with pistachio and then go to cashew,” Greene says.

The team has since tried this strategy with walnut and pecan, which similarly cross-react. Walnut is also considered the more “potent” allergen, she says. Walnut desensitization has been shown to potentially lead to pecan desensitization, but not the other way around.

But by having patients who failed walnut OIT go through pecan first, they were later able to successfully conquer walnut OIT, she says.

The study was presented at the 2025 AAAAI/World Allergy Joint Congress in San Diego.