It sounds like an allergic reaction, not acne. Acne doesn't occur spontaneously. If you're itchy and getting a rash (that looks like acne) then you're allergic to what you're eating.

As a licensed esthetician, I can tell you that actually yes, some foods for some people do cause an acne like response very, very quickly. Usually, I would see it in clients who had gone on a big shrimp/shellfish eating binge that they weren't used to. They would be astounded that I could tell but in that case, it's the iodine. Some people, even those not terribly allergic, will break out from eating an overload of shrimp. My eldest daughter breaks out with cystic acne flares from eating rampant canned salmon. I don't know if iodine is a constituent of salmon or if it is something else. She is not allergic to salmon but she cannot eat a can or two a day as she was doing. Allergy is something to be tested for, don't misunderstand me please but there are some things that some are sensitive to in higher quantity than others that absolutely will present as an acne flare extremely quickly on the face/body and cystic acne can have mild itching as well. Be allergy tested for salmon, coconut, tree nuts and iodine. I wouldn't recommend continuing to try eating fish and coconut until you know more. Go from there and good luck!

If you're new to Paleo, it could be "dieters acne". Sudden and dramatic changes to the diet can stress the body, triggering an acne breakout.

Secondly, you mention that you are eating canned salmon on a daily basis. This is sort of a long-shot, but could the Bisphenol A be the culprit? Acne is often hormally triggered and BPA is an endocrine disruptor (i.e. upsets our sex hormones), which is used as an industry-standard canning sealant. You also mention taking fish oil. Fish oil helps the body fight inflammation, and so in many cases is useful when dealing with acne, which is an inflammatory disease. However, some people also find fish oil can trigger bad breakouts. Find out which group you belong to.

If you're not already, keep carb levels moderate to low and consider supplementing with zinc, which will improve wound healing and bolster your body's immune system. Finally, remember that Paleos as a group tend to be very nutrition orientated. Your acne may be completely unrelated to your diet. For example, do you use only non-comedogenic personal hygiene products? Do you take long, hot, showers/use steam baths or saunas? How often do you wash your pillowcase?

I'm allergic to tree nuts, including coconuts. It's a really annoying and unfortunate allergy that I hope is the result of wheat protein cross-linking and thus will fade over time. Anyway, when I eat nuts or coconut, I get a reaction in my mouth and a slight swelling of my gums, plus probably a similar reaction all the way through.

I am a 45 year old woman and have been battling cystic acne since I was a teenager and with all the trial and error I have done with changing my diet over the years, I can absolutely say with certain that gluten, nuts and seeds, and yes coconut, and even avocado will cause my skin to breakout in cysts - within just a day or two of eating any of the items. The cysts are not an allergic reaction, they are acne; after a day or two, the whitehead comes to the surface. PLus trust me, I know acne when I see it as I've dealt with this since I was 14.

I have tested this numerous times, particularly with coconut products and avocados, eating them when my skin is clear and I have not eaten anything else that could be suspect, and every time big whopping cysts on my chin, cheeks, and forehead.

So trust your skin and your intuition about your body. If you feel a food, even one that is supposed to be so healthy and wonderful, is causing your skin to break out, it probably is.