Auto immune reaction causes inflammation causes acne? Being sick depresses immune function / directs immune function elsewhere causes reduction in inflammation causes reduction in acne?

I wonder if a mechanism comparable to the above could be at work.

Your body detoxed when you vomited or fasted/ate less food. Acne is caused by a problem with gut flora. Too much candida. Your acne may be an allergic response or a toxicity overload. Look at an acne face map. Here is a good source, http://www.skinacea.com/acne/acne-face-map.html#.UOE8K4l5mc0 and look at the hours those correlating organs are in full function, http://www.astrodreamadvisor.com/Qi-Cycle.html# and http://www.silenthealingcenter.com/site/section/nutritional_program/organ_cycle.php . I currently have acne that stemmed from medicinal and health issues causing bad food intolerances. A dietary change, from gluten-free to grain, sugar, dairy, soy-free caused my acne, and although I feel better, I know my insides are saying otherwise, hence the breakouts. I read on a GAPs diet by dr Cambell Mcbride, that when candida overgrowth damages the gut lining, it creates a leaky gut and your blood reacts to larger food particles by overreacting (aka allergy or food intolerance. Food intolerance can mean that your body does not react, nor digest and allows the food to spoil, creating toxins that come out via skin or like an allergic reaction). Skipping meals and vomiting detox your body but does not cure it. Too much meds (all that I know of are fungal based) can cause acne as well, another reason candida is a culprit. This is long winded, but here are some ideas: baking soda water 2 hrs before breakfast (no more than 1 tsp a day! Unless you want acid reflux to the extreme). Baking soda maple syrup is supposed to act like a poison in killing off candida in the stomach. An apple fast for 3 days. AppleCiderVinegar (ACV) is supposed to be good but no such luck for me. Add garlic and other anti fungal foods to diet. And if you are extreme, honey and dates as your only sugar source. Your body needs sugar, and if you don't eat it, it will pull sugar from other sources. Honey and dates have anti fungal/bacteria qualities, so long as they are raw and unfiltered. You saw an improvement because you detoxed, which is a good sign that you can cure your acne by a wompen dose of live probiotic and a candida cleanse. Hope this helps! Not a doctor, just feel your pain.

Skin inflammation will go down overnight/over time after sleep/rest, regardless of whether or not you have some sickness. The inflammation has got to go down eventually.

One guess: when you throw up, you are going low carb and/or removing acne triggers from your diet.

Acne not only commonly affects face but also the chest, back and neck. It is required to use Azelaic Acid cream which treat against moderate acne as well as rosacea.

Could be the fasting that occurs when you're sick (throw up, don't want to eat, etc). Perhaps try fasting when you're not sick (water or fresh-pressed vegetable juice), and see what happens. If your acne gets better in a similar way, you've found an important data point.

My skin does the same thing. I still (usually) eat normally when sick. Frankly, I suspect that your body has bigger fish to fry and ignores skin issues and attacks the sickness. Or perhaps your white blood cell count goes up and clears up skin issues before there is a problem. Just a couple guesses.

I think the acne has more to do with you not exercising and possibly less oil produced when you are inactive, eating less, and sick.
If i were you i would get a spectracell test for antioxidant function. Acne and antioxidant function are closely correlated. Your body is most likely not detoxifying and free radicals are hurting your skin cells.