Stanley Cup Mold: Is It True? An Expert Doctor Reveals 9 Signs To Watch For

Updated: Apr. 11, 2024

A doctor specializing in immunology and infection responds to recent social media reports and offers smart tips to safeguard your sips.

Stanley cups are beloved by thousands of the wellness-obsessed, from celebrities (see Exhibit A: Olivia Wilde) to the reported Target employees who were disciplined for loading up on inventory before new product hit shelves for customers.

Adored for their size, cold temperature maintenance and the eye-pleasing colors that seem to inspire users to stay well hydrated, Stanley cup sales were projected to surpass $750 million in 2023, according to CNBC. At 111 years old, the brand is hardly a passing fad: It was founded in 1913 by Brooklyn-born physicist William Stanley Jr. with his invention of the all-steel vacuum bottle.

But with modern-day popularity come a unhygienic concern that’s been alleged on TikTok about Stanley tumblers: Mold growth in these buzzy beverage holders. Purvi Parikh, MD, an allergist and immunologist, took a careful look to respond.

Mold Stanley cups: Here’s the science

Mold is a type of fungus which the Centers for Disease Control and Prevention notes is an ever-present part of our environment, having been on the Earth for millions of years. Mold enters our homes through open doors and windows and even hitchhikes on our clothing, shoes, and pets. In all these cases, moisture is what causes mold growth.

Dr. Parikh explains that since Stanley cups are used for liquids, “humidity is common…especially inside the cup, where there isn’t any ventilation.” She points out that the crevices inside the lid are particularly susceptible to mold, as these tiny nooks can harbor mold spores if they’re not cleaned meticulously. Arguably, that’s true for just about any travel beverage holder with a lid.

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How does mold affect us?

On the immune system impact of mold exposure from everyday items like Stanley cups, “A one-time exposure may not be an issue,” Dr. Parikh says. Repeated encounters with mold are more likely to lead to a range of health issues. According to Dr. Parikh, these include:

  • Allergic reactions, evidenced by a stuffy nose or a sore throat.

  • Asthma symptoms, such as coughing, wheezing, or shortness of breath.

  • Gastrointestinal discomfort, including stomach aches, diarrhea, and vomiting.

  • For those who are immunocompromised, there’s an increased risk of infection.

Certain groups are particularly susceptible to the effects of mold exposure. These include:

  • Children, whose immune systems are still developing.

  • Immunocompromised individuals, those whose immune systems are weakened due to conditions like HIV, cancer, or the use of certain medications.

  • Individuals with asthma or Chronic Obstructive Pulmonary Disease (COPD).

  • Those with pre-existing allergies.

  • Pregnant women, who need to be extra cautious due to changes in their immune system.

Dr. Parikh emphasizes that if you suspect a reaction to mold, it’s crucial to immediately stop using the cup, clean it thoroughly, and consult a board-certified allergist for testing.

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What are the best practices for preventing mold growth?

“Wash it daily even if only using it for water, as water can cause mold growth too,” advises Dr. Parikh.

When you clean your Stanley cup, it’s essential to disassemble your product completely—this means separating the straw, lid, spout protector, and any other removable parts. To ensure a thorough clean, use warm water mixed with dish soap, paying extra attention to these often-overlooked nooks and crannies.

In cases where visible mold has already made an unwelcome appearance, experts have a go-to solution: Distilled white vinegar or hydrogen peroxide. Apply your choice of cleaner to the affected areas, let it sit for five to 10 minutes, and then rinse thoroughly.

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