randomly during your travels you will get this message
you now have a random mutation that you can see in your character screen>trait section

You have a few options
1. go all the way into the snowy area to a workshop and trade 10 small medals for a potion (very expensive)
2. Invest in healer merchants and hope they have it in stock
3. throw trash into trash cans and acquire 4200 recycle coupons (insanely grindy)
4. Go to the casino to gamble THIS IS THE BEST OPTION

Travel to Palmia
it is located beyond the central river, just before the snowy area

Head into the building with the Dice decoration on top, it is located at the south eastern part of the city.

Enter it and use the teleporter, then go into the central teleporter

Play hoops to earn a few casino chips, they are free to play but cost stamina. Make sure you have food since you'll be here for a while

Once you have a few chips, go to the blackjack tables

You can bet up to 1000 chips at once, with double or nothing, I recommend you start betting 10 or 100 until you have enough chips

The AI will always stop hitting cards if they are 17 or above, so exploit that
If all else fails, you can always savescum

The Prize Clerk is located here from the central teleporter

The potion costs 3000 chips and restocks every 5 days, making this an easy and unlimited source of cures.