Brief Answer:
Information

Detailed Answer:
Hello,

This could be from the prednisone. Usually a short course as you were on doesn't adversely affect the immune system, but it definitely can. What prednisone does is turn down the immune system so that there is less inflammation. The down side of that is that when a person is no longer taking it, allergic symptoms can come back and often be stronger, but that should resolve back to your "baseline" allergic activity levels after your body readjusts.

Now about the low grade fever, muscle cramps, and fatigue, this can be a sign of adrenal suppression. When taking an exogenous corticosteroid (steroid taken as medicine), the body turns down it's own production of cortisol. It thinks "we have plenty of cortisol" so the releasing hormone from the pituitary/hypothalamus in the brain turn down, telling the adrenal glands to make less cortisol. Usually when this happens, it occurs when people have been taking corticosteroids like prednisone for a longer time than you have. But you may be quite sensitive to it's effects. Your own adrenal function will likely return to normal soon, but in the meantime, avoid excessive activity, getting cold, going without food, or other things that stress your body. Because stressors on your body will require higher amounts of cortisol, and you may not be able to make that right now.

The other possibility of what might be going on is that you caught a viral respiratory infection right now that is causing the low grade fever, myalgias, and fatigue.

If your symptoms continue, go to your doctor to have an ACTH level drawn (adrenal cortico-tropic hormone). This is the hormone from the pituitary that I described that may have turned down due to having taken prednisone. It would be good to know if that is what is at play here.

I hope this information helps. Please let me know if I can provide further information.

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