We need more details to help you.
What were the investigations done and their findings at the age of 2? Its unlikely for allergy alone... as loss of hair and weight loss
are not seen in allergies.
The last winter episode looks like hyper reactive airway disease
. What was done for that?
What are the present problems other than fatigue
and loss of weight?
What is her present weight and height? How is her mentation? Any family history of significant illnesses? what is her complete blood count- Hemoglobin
, white cell count, Platelets, ESR, Peripheral smear?
Where there any significant findings on examination like liver or spleen enlargement or lymphnode enlargement?
How is her food intake?
Have you checked her thyroid
profile any time?
The three episodes may or may not be related. But she needs a proper evaluation- detailed analysis of history, detailed physical examination and investigations as needed.