It is definitely no treat — but could be a deadly trick, a fatal one played by nefarious drug dealers on youths and young adults.

Illicit fentanyl pills are being trafficked in bright “rainbow” colors and even in holiday baggies. But don’t be fooled.

This Halloween season, and well beyond that, the dramatic spike in fentanyl use and overdoses must be on everyone’s radar. It could be a matter of life or death.

This month alone, there have been at least five fentanyl deaths on Oahu — and concern is high that the numbers will rise, based on deaths correlating to amounts of the drug that Hawaii is starting to see, said Hawaii’s U.S. Attorney Clare Connors.

Law enforcement officials and the Drug Enforcement Agency are sounding the alarm, loudly. This week, a Pearl City man was charged for supplying fentanyl that led to the Oct. 9 death of a “young resident” in Hawaii Kai; allegedly found in the suspect’s unit were stashes of fentanyl powder and crystal meth, plus rifles and loaded rifle magazines.

Late last month, Hawaii’s federal drug task force warned about an extremely potent batch of fentanyl that had been smuggled onto Hawaii island. In just one week, police there said, the drug was believed to have killed three people and caused several more overdoses.

Fentanyl is a synthetic opioid that is 50 times more potent than heroin and 100 times more potent than morphine, the DEA warns. Just two milligrams of fentanyl — equal to 10-15 grains of table salt — is considered a lethal dose.

“One pill can kill” is the dire warning — but also know that many deaths are attributed to fentanyl mixed with other illicit drugs like cocaine, methamphetamine and heroin. Many users weren’t even aware that they were actually taking fentanyl.

Increasingly, anti-drug officials are advocating that the nasal spray Narcan (naloxone), an emergency antidote against fentanyl overdose, be more readily available at schools.

A scary reminder of the thriving fentanyl trade came Wednesday, when authorities seized thousands of suspected fentanyl pills hidden in candy boxes and baggies at Los Angeles International Airport. Inside the Sweetarts, Skittles and Whoppers boxes were fentanyl pills, with officials seizing about 12,000 pills in the bust.

It’s also clear that drug traffickers are targeting young people, using emojis and slang as coded messages to market and sell drugs via texting and social media. The near-term concern, of course, is that “rainbow fentanyl” or “candy” boxes of the drug will show up in the Halloween bags of innocent children.

“Parents need to make sure they are checking their kids’ candy and not allowing them to eat anything until it has been inspected by them,” the L.A. Sheriff’s Department warned.

Crucial advice indeed, as law enforcers and Hawaii’s citizens try mightily to beat back yet another danger in our communities.