My mother has some strange things going on with her. Here's some background info that may or may not be relevant:

Several months ago, she stopped taking Dilantin (for hormone-related seizures that she doesn't have anymore since she in menopause) but had been on it for a 2 decades up to that point.

Dilantin is well known for causing liver damage.-

She recently had a hysterectomy.

She has been under a huge amount of stress since retirement last summer, move to a new state, and building a new home (which has been fraught with problems).

Starting a couple years ago, she began having some numbness/tingling in parts of her lower legs (ankle - top of foot, I think).

Has she been checked for diabetes?

About 4-5 months ago she began breaking out into large hives, every day, all over her body in shifting places. They come and go. Some days better than others. Taking antihistamines helps a bit but hardly stops it. She can't pin it to a reaction to any particular food. She's just dealing with it as best she can.

She should focus heavily on her adrenals for this.  Hives can be from allergic reactions but also stress induced.  The adrenals counter allergic reactions and help us deal with stress.

She began having occasional migraines last month.

Migraines can have a lot of triggers, including hormones.  In her case this is very likely, but she should still keep a migraine log to see if there is a common denominator.  Certain foods for example containing amines or sulfates or allergies.

For the last week, she has lost most of her sense of taste. Dr. says it's probably a viral infection on her tongue (she has no other symptoms with her tongue).

There are several things that can cause this.  Most often it is from a zinc deficiency and sinus infections can also cause this.  But there is another possibility in her case that is more likely.  Low estrogen.  Estrogen increases the sense of smell and taste.  The sudden drop in hormones from the hysterectomy could have caused this.  And with the hysterectomy her adrenals would be her primary source of hormones right now.  But those sound like they are shot right now.

I'm concerned about these strange and seemingly unrelated issues she's having. I wonder about poor liver function after the Dilantin therapy as well as adrenal weakness with the stress.

Both could mess with hormone levels.

She has ordered your Adrenal Tonic and has used it a bit (not as regularly as she should), because she gets worried when the hives flare up, thinking she might be reacting to something in the formula. I wonder about her hormones since the hysterectomy (her Dr. wants to put her on bioidentical, which I told her are not really bioidentical).

Nor safe.  The hormones could just create whole new imbalances.

Are bitters and Adrenal Tonic a good place to start?

Yes, particularly the Adrenal Tonic.  Also remember a diet high in vitamin C rich foods and pantothenic acid, not stimulants, watch the stress, etc.

Can stress do all of this?

Yes, stress weakens the adrenals even more, which are her primary hormone source right now.  Weak adrenals also contribute to the hives and even more stress as the adrenals also produce our anti-stress hormone.

I'm glad she's off the Dilantin at least. Would coming off of Dilantin after being on it for a long time be likely to cause imbalances?

I don't think this has much to do with it.  I still think the most likely cause is the sudden drop in estrogen and hormone imbalances after the hysterectomy being compounded by the adrenal dysfunction.

Sorry - I know you're busy. I'm trying to connect dots and see a bigger picture, but I'm just not smart enough. Her various doctors haven't helped much either.