Patient aged 57/f having cough since 8 months. Sputum test was done and chest x-ray was done but nothing came out.A cough aggravated on having fruits or after eating anything, more in the night. Wheezing present on examination. She took all kind of medicine with the home remedy.but didn't get any result. The patient is on medication for hypertension, hypothyroidism since 20 years.

She is also having xanthelasma. What could be the cause? What tests are required?