In Unani medicine, Fasd or venesection is a bloodletting procedure used for therapeutic purposes.
However, it is contraindicated in cases of poisoning and in patients suffering from plague.
This is because making an incision for bloodletting can lead to the rapid spread of toxins throughout the body.
So the assertion that Fasd should not be done in poisoned patients and plague is true.
The reason given — that its toxicity will spread if Fasd is performed — is also true and directly explains the contraindication.
Therefore, both statements are true and the reason correctly explains the assertion.