Hi! Yes, an overgrowth of the Candida fungus - which we all have - is a common side effect of steroid treatment.
I had not heard of the L-Lysine, but give it a try.
Salt water mouth gargles are also good. Be sure to spit out.
If you have the thrush in your mouth, then you also have overgrowth in your intestines. It is common for women also to get a vaginal yeast infection (candida again). So a more thorough treatment is to take a good probiotic supplement - there are several on the market, yogurt with extra probiotics, Lactobaccillus GG (very good and very spendy).
Reduce the sugar in your diet to zero if possible, for a while. Fungi feed on the sugar.
Plus, if the things above are perectly effective, I would recommend a course of mycostatin (Nystatin) from your doctor. This will be the most effective at erradicating the yeast from the entire digestive tract.
Quix
I got it from Asthma inhaled steriods. Yuck!
In my own experience, I have taken oral steroids 3 different times. I have gotten thrush every time. So I'm sure that IV steroids can cause thrush also. My PCP's nurse advised me to take L-Lysine. It helped a lot, mostly gone in a couple of days. I'm sure others will chime in on this too. Also in my case rinsing with saltwater helped. Good luck, sorry about the recurring cold, the same thing happened to me, and I didn't go jogging or camping!