A federal agency posted a critical public health alert on Monday about over-the-counter cannabidiol (CBD) products. The message from the Food and Drug Administration (FDA) is important and timely: If you think there’s no risk in trying CBD, think again.

“CBD has the potential to harm you, and harm can happen even before you become aware of it,” the federal agency warned this week as it continued its crackdown on companies marketing these products.

CBD products, which many consumers believe can ease pain or anxiety, flooded onto the market after a 2018 federal law change was widely perceived as loosening restrictions on sales of products containing hemp compounds, such as CBD. Hemp and marijuana are the same plant “taxonomically speaking,” according to North Carolina State University experts, but hemp contains 0.3% or less of the active ingredient that delivers marijuana’s high.

Stores selling CBD oils, syrups, creams and other products have popped up in strip malls in Minnesota and across the nation. Gas stations and some grocery stores feature displays at the checkout counter. Pet stores push CBD products as a remedy for anxious companion animals. It’s easy to see why BDS Analytics estimates that the market for such products will “surge from $1.9 billion in 2018 to $20 billion by 2024, a compound annual growth rate of 49%.”

The safety concerns detailed this week by the FDA should give plenty of pause to the legions already using CBD or wondering about it. Among the known risks: liver injury and serious interactions with other drugs. Side effects can include drowsiness, irritability and diarrhea.

The agency also warns that medical research is far from complete and that many serious questions remain. For example, it’s unclear what CBD’s effects are on children, pregnant moms and the elderly, especially with long-term use. Cumulative exposure from using multiple CBD products at the same time — such ingesting it or using it on your skin — carries unknown risks.

In addition, laboratory studies on animals also suggest that CBD could potentially affect men’s fertility. Changes documented include a “decrease in testicular size, inhibition of sperm growth and development, and decreased circulating testosterone.” Research like this doesn’t necessarily mean CBD would have the same effects in humans. But these early findings are a troubling reminder of all that remains unknown about CBD.

Another concern: manufacturing quality and purity. The FDA warns that “lack of process controls” carries risks. The agency said it is investigating reports that some products have contained heavy metals, pesticides or the active ingredient found in marijuana. Part of the agency’s crackdown on CBD companies last week included sharply worded warning letters to leading firms. It said the companies are illegally selling these products and set a 15-day deadline for a response. Failure to make corrections could result in “legal action, including product seizure and/or injunction.”

The FDA’s work to sound the alarm on CBD comes in the wake of its strong efforts to stem the epidemic of e-cigarette use among teens. The agency’s willingness to wield its regulatory muscle is commendable, especially when deregulation has been a Trump administration priority.

But consumers also need to do their part. That means seeking out credible information on CBD instead of blindly accepting claims made online or from fly-by-night retailers. Cure-alls have been hawked through the ages. Skepticism is always healthy.