Candida is one of the biggest quackery in the alternative health world. Systemic Candida infections don't happen in people with healthy immune systems. And with healty I mean better than HIV patients or people undergoing chemo.
Candida hypersensitivity/syndrome has also been studies. The two review papers I looked at concluded there's no evidence for it.
That said, Candida can cause acne. But it happens through local infections in the bowel and the skin. Bowel infections can cause bacterial imbalance and leaky gut, and these can aggravate acne.
Skin infections can cause the skin immune system to over-react (it's a bit trigger-happy in people with skin conditions) and cause acne that way.
But neither of these conditions is mysterious. Doctors can easily diagnose both skin and bowel infections. And they both can be treated easily.