A version of column was published in USA Today on April 2, 2014.

Patients in my clinic increasingly use health apps on their mobile devices.  Many of these apps track various health metrics, such as weight or calories eaten, while others go a step further and help patients make sense of their symptoms or even suggest diagnoses.  It’s estimated that 500 million people worldwide will use a health app by 2015, with the health app industry becoming a $26 billion business by 2017.  Despite the popularity and promise of these apps, I’m not yet ready to “prescribe” them to my patients.

The sheer number of health apps is staggering, with over 40,000 apps categorized as “Health & Fitness” or “Medical” in Apple’s App Store alone.  But how many are actually useful? The IMS Institute for Healthcare Informatics found that fewer than 25% offered patients legitimate medical information. Not many physicians offer guidance for health apps, leaving patients alone to confront an ocean of apps of uncertain relevance or usefulness.

Some apps can even be dangerous.  Consider those that claim to diagnose melanoma, a lethal form of skin cancer, by taking pictures of suspicious moles and analyzing them.  A study from JAMA Dermatology looked at four such apps, and found that three of them misread actual melanomas as “unconcerning” 30% of the time.  Patients falsely reassured by these apps may delay appropriate care with tragic consequences.

And it’s not just skin cancer apps.  One study broadened the search to include all cancer-related apps and found that more than half of them did not contain scientifically validated data.  Another concluded that only 13 of 49 apps designed to help educate and treat patients with peripheral vascular disease had any involvement from a medical professional.

Recognizing the threat of rampant, unregulated medical apps, the FDA moved to oversee select categories of health apps last year, but it’s still a strikingly small effort: To date, only about 100 apps, out of tens of thousands, have received FDA approval.

Perhaps most concerning, health apps have profound privacy and security concerns.  Consider free apps, which generally rely on advertising for revenue.  They are not bound by strict patient privacy laws that govern traditional medical care and may share patients’ sensitive information with advertisers.  According to Joseph Hall, chief technologist at the Center for Democracy & Technology, “Such collection, use, and disclosure of information may be beyond what patients reasonably expect given anticipated uses of the technology.”

Privacy Rights Clearinghouse, a consumer advocacy non-profit organization, looked at both free and paid health apps, and found that 72% of them had security and privacy risks, including connecting the third party sites without a user’s knowledge or sending health data without encryption, making it vulnerable to hackers.

U.S. Secretary of Health and Human Services Kathleen Sebelius has said that mobile health is “the biggest technology breakthrough of our time” and imagines a future where control over patients’ health will always be within hand’s reach.  Reaching that goal requires testing apps in clinical trials to prove their effectiveness, similar to how we study drugs and medical procedures before administering them to patients.  Furthermore, apps that store patient health information need to adhere to the privacy and security regulations set by the Health Insurance Portability and Accountability Act, which governs patient information in the hospital or clinic.

Only once these standards are met will more physicians recommend them to patients.  That is when the true potential of mobile health apps will be realized.

Kevin Pho is an internal medicine physician and co-author of Establishing, Managing, and Protecting Your Online Reputation: A Social Media Guide for Physicians and Medical Practices. He is on the editorial board of contributors, USA Today, and is founder and editor, KevinMD.com, also on Facebook, Twitter, Google+, and LinkedIn.