Hello,
It can be due to seborrheic dermatitis, eczema or rosacea. Eczema is a form of chronic dermatitis (rash).Allergic reaction is one of the important causes of eczema. Allergic reaction can occur to strong soaps, Solvents, chemicals, certain foods, food additives, plants, metals, cosmetics, even urine and faeces of some animals (dust mites).
Seborrheic dermatitis is a common skin condition that causes flaky,dry, white to yellowish scales to form on oily areas esp under the nose or anywhere on face. People with seborrheic dermatitis produce too much sebum (the natural skin oil).
I suggest you to get it evaluated from a dermatologist. It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
The area around your nose looks like psoriasis. Look up some images of it and see if you can relate. It is a more severe form of eczema. Can be caused by stress or change in environment. Hope that helps!