The pH of lantus has been adjusted so that it's not as soluble in body fluids... this gives its even long acting quality. Its acidity is higher than other insulins which could be causing the reaction. The itchiness stops for some people after using it for a couple of weeks.

You should never mix lantus with other insulins or even inject in the same area because it may cause the lantus to become inactive.

Sometimes long term insulin use can cause fatty bumps called lipohypertrophy but it sounds like you've had an allergic reaction or a reaction to the acidity.

Glad to hear the novolin's working for you

Take care (c;