Dear sir i can understand your concern usually insulin will have some preservatives which might be the reason of allergy in some individuals to control sugars in diabetes insulin is only option kindly let us know about condition your mom in detail like duration of diabetes height and weight. pls tell us how many times you took that injection and when did itching appear. i would also want to know where did the itching first started? there is a procedure called desensitisation to reduce insulin allergy this can be done in hospital settings only. Hope I was able to help you. If you have any further question feel free to write me back. I will be happy to help. Take care. Best Regards. Dr Vamsi Krishna Consultant Diabetologist Apollo Hospitals