Can allergies (eg. peanut) and diseases (eg. ceoliac) occur more these days or are just more aware?

Occur more: You might want to check out information about the "hygiene hypothesis" as a possible explanation, but there is evidence that allergies are becoming more prevalent.

Both: The incidence of gluten sensitivity/celiac disease is increasing and with screening high risk populations, there is more awareness. This can identify individuals who have subclinical disease. For peanut allergy, the incidence is increasing (from 0.5% of the population to 2% over the last 15 or so years). Similarly, there is greater awareness of food allergies in general.