You might be wondering, “I took a hot bath and now I feel sick.” This is an all too common reaction to hot water. During the last week, I’ve been having this problem for several weeks, and I was convinced it was a cold! It turns out that it is a sign of a heart problem! Let’s look at the possible causes. A hot bath could cause dehydration, or it could be a symptom of an underlying health condition, like thyroid disease. It’s always best to seek medical advice before trying any home remedies.