Chef Michael Chiarello at the 2015 Food Network & Cooking Channel South Beach Wine & Food Festival.Photo:Ilya S. Savenok/Getty

Chef Michael Chiarello poses at the KitchenAid Culinary Demonstrations during the 2015 Food Network & Cooking Channel South Beach Wine & Food Festival presented by FOOD & WINE at Grand Tasting Village on February 21, 2015 in Miami Beach, Florida

Ilya S. Savenok/Getty

ChefMichael Chiarellodied following an acute allergic reaction which led to anaphylactic shock, but the cause of the allergic reaction is unknown.

“The doctors don’t know what caused the allergic reaction and neither does the family,” a representative for Gruppo Chiarello tells PEOPLE. “They may never know.”

Chiarello, a former Food Network star, died at the Queen of the Valley Medical Center in Napa, Calif. on Saturday after being treated for the allergic reaction for a week, according tostatement shared with PEOPLE. He was 61.

Dr. Inderpal Randhawa, CEO and founder of theFood Allergy Institute, tells PEOPLE that a person being unaware of a life-threatening allergy later in life “is rare but it does happen.”

“Two-thirds of adults with food anaphylaxis develop the disease after 18 years of age,” says Randhawa, who did not work as Chiarello’s doctor.

Dr. Randhawa gave an example of an older person developing an allergy that initially resulted in “atypical symptoms such as abdominal discomfort or skin rash.” If the person modified their diet but “over the next year, they continued to cook shellfish where there are allergens in the air, the air-based allergens will increase sensitization of their immune system and increase their risk of anaphylaxis,” says Dr. Randhawa. “The next time they consume shellfish, it can result in a severe and rapid reaction.”

The medical director of pediatric pulmonology, clinical immunology and allergy at Miller Children’s Hospital in Long Beach, Calif. also noted that “several factors make allergic reactions worse” including autoimmune diseases, blood pressure medications and erectile dysfunction medications.

“Having several factors combined at once during a small food allergen exposure can result in a life-threatening event,” said Dr. Randhawa.

An autopsy report could “identify the general groups of foods to which he might have had a reaction,” Dr. Randhawa. But a representative for Chiarello did not clarify to PEOPLE if an autopsy report is being conducted.

Michael Chiarello in 2015.Ilya S. Savenok/Getty

Michael Chiarello, Celebrity Chef and Former Food Network Star, Dead at 61

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After Chiarello’s death, his family said in a statement: “We deeply mourn the loss of our beloved patriarch Michael. His culinary brilliance, boundless creativity, and unwavering commitment to family were at the core of his being. He brought people together through the joy of shared meals, fostering lasting memories around the table."

The California native was born in the Northern California city of Red Bluff in 1962. At 25 years old in 1987, he opened his first restaurant Tra Vigne, in Napa Valley, perBusiness Wire. The opening of Tra Vigne was followed the his additional Napa Valley eateries, Bottega, Ottimo, and Coqueta — which has a location in Napa Valley as well as San Francisco, according to theSan Francisco Chronicle.

In addition to opening several restaurants, the chef created Chiarello Family Vineyard and joined the wine industry in 1999,according to his website. At the start of the millennium, he then established a retail line of artisanal foods, kitchenware, and home products, titled NapaStyle.

Michael Chiarello.Dave Kotinsky/Getty

Michael Chiarello, Celebrity Chef and Former Food Network Star, Dead at 61

Dave Kotinsky/Getty

While the chef created several restaurants and the Chiarello Family Vineyard, he was known for hosting several shows that aired on PBS, Fine Living and Cooking Channel, and his Food Network series,Easy Entertaining With Michael Chiarello, which ran for 10 seasons and earned Chiarello an Emmy award. He also appeared as a guest chef on theTodayshow andThe View, per his website.

Chiarello’s funeral arrangements will be private, and in lieu of flowers, his family is asking donations instead be made toMeals on Wheels.

source: people.com