This seems a pretty good description of a "nursing strike".  This occurs
typically in mothers who have alot of milk.  Around 3 months, the baby
starts to refuse the breast, as described.  But, regardless of how they
refuse the breast when awake, they will often take it when half asleep
or if the mother walks around with him.  Also, they tend to nurse very
well at night.  Surprisingly, the babies continue to gain weight.

If this fits, the best approach is not to try and force the baby to take
the breast, a futile strategy in any case.  Even though these babies
will suck their hands, they would rather do that than nurse.  Let them
suck their hands.  Usually, eventually, it gets better, though it may
take some weeks.

The other possibility is that the mother's milk supply has decreased.
This occurs around 3 or 4 months in some mothers, for no obvious reason.
I find this a good place to use domperidone (or metoclopramide) and
herbs such as fenugreek and blessed thistle.

I doubt allergies or ear infections or thrush cause this problem.

Jack Newman, MD, FRCPC