Mpox manifests in a variety of ways, progressing from systemic symptoms like a fever and swelling to dermatological symptoms like lesions. These lesions are the most common symptom of mpox, and can look similar to pimples or blisters.
But they aren’t pimples or blisters. Mpox lesions have unique characteristics that can help you distinguish them from other dermatological conditions, though a healthcare provider should help you make the final determination.
Stages of an Mpox Rash
According to the Centers for Disease Control and Prevention (CDC), mpox lesions evolve through four stages, each of which lasts about one to two days. These stages are:
Macular (a flat lesion)Papular (an elevated lesion)Vesicular (a fluid-filled lesion)Pustular (an inflamed, pus-filled lesion)
After that, they scab and flake. The total duration of an mpox illness is usually between two to four weeks.
You’ll Probably Have a Fever First
The onset of mpox symptoms is similar to the flu, meaning it will likely start with a fever, according to the CDC. So if you have new bumps or blisters but feel otherwise healthy, there’s a good chance your skin is reacting to something other than mpox.
The flu-like symptoms start about three weeks after mpox exposure, and the rash may begin between one to four days after that.
You Won’t Be Able to Pop Your Initial Bumps
A new mpox bump isn’t poppable at first. If you can pop any bumps that have appeared on your skin within four days, they’re likely not mpox, Christine Ko, MD, a professor of dermatology and pathology at Yale School of Medicine, told Verywell.
Ko doesn’t recommend that people scratch at new bumps and blisters. But a gentle scratch test may offer some clarity if you’re not sure whether or not the rash is from mpox.
“If you gently scrape at that very initial lesion with your fingernail and it feels firm, and does not pop with gentle pressure on it, I would be more likely to be concerned,” Ko said.
The CDC describes these initial mpox lesions as rubbery and deep-seated.
Lesions Will Be Small and Painful
For the most part, new mpox lesions are pretty tiny—ranging from the size of a piece of rock salt and grain of rice, Ko said.
“They can be pretty inconspicuous to the untrained eye,” she added. “Some of them could be ‘pea’ sized. But on average, most seem to be about the size of a grain of rice or smaller.”
These small bumps can become quite painful over time. According to Lida Zheng, MD, dermatologist and assistant professor of dermatology and medicine at Northwestern’s Feinberg School of Medicine, patients seem to experience more mild discomfort or no discomfort at all when lesions are flatter and first appear, and more pain as they fill with fluid and grow.
“Patients report pain differently, but any opening in the skin can definitely be sore,” Zheng said. “Lesions in areas like the genitals or the anus can be especially sore when patients are urinating or having bowel movements.”
As lesions start to heal, they tend to become itchy.
Lesions May Cave After a Week
Zheng says that once lesions become more pustule-like during the fourth stage, they’ll start to cave in towards the center, mimicking the shape of a volcano. This can take about five to seven days from when the lesions initially appeared.
“This central depression is technically called an umbilication,” Zheng said. “Basically, it’s having a little divot.”
Zheng added the timing of this indentation can vary, and it might not happen to everyone.
What to Do If You Suspect You Have Monkeypox
If you have a rash you suspect is mpox, get tested. Most primary health care providers, dermatologists, and even some urgent care centers know how to swab for mpox, Zheng said. She recommends people see whichever provider is most accessible to them.
You can learn more about how to get an mpox test here.
Prior to getting tested or treated, you may be able to book a video appointment where you can point out your symptoms, or send a photo for a trusted professional to evaluate.
In the meantime, considering isolating yourself and keeping your rash clean and covered.
“Apply a little bit of Vaseline or Aquaphor and a wear a bandage to cover the lesions,” Zheng said. “Keep the areas moist and clean to help your skin heal and prevent infection.”
