A few Kratom users, those more sensitive than others, have had allergy-like reactions to Mitragyna speciosa Kratom, especially in higher doses, which causes them to feel a generalised body itching, similar to opioids. This unpleasant sensation is most likely due to histamine output, and can be treated with histamine medication (dph/dhm) if it becomes too uncomfortable.
When using Mitragyna speciosa Kratom reasonably, health problems are unlikely, unless one is consuming large quantities of Kratom every day, or combining Kratom with other substances.
Potential side-effects of Mitragyna speciosa Kratom use can occur, such as nausea, constipation, sleep problems, and temporary erectile dysfunction, but they are all temporary and dose related, disappearing as the effects of Kratom fade away.
Like with any other drug or medicine, people's reactions vary, and some people could possibly have an allergy related or other unusual reaction to Mitragyna speciosa Kratom, even if Kratom has been used responsibly. This is why it is always advised to test one’s sensitivity to Kratom by starting low, and progressively increasing dosages.
However, some reports point at seemingly more severe problems from extensive daily consumption of Mitragyna speciosa leaves, by Kratom users in South-East Asia, and Thailand especially.