yeah, I'd check out the parasite angle, as you just eliminated the fungus/bacteria angle.
However, you might look into two more possibilites.
1. Allergy reaction. Are you possibly reacting to an allergen?
2. Missing enzymes/fats. Are you getting the enzymes and fats you need in your diet? Your body needs saturated fats to process properly - are you consuming enough/any? Coconut oil is a vegan friendly saturated fat. Or you could be missing key enzymes that your body needs, and so your skin and intestines are trying to desperately shed food wastes from you anyway it can.