We have 5 girls ranging in age from almost 5 years down to 15 weeks old. All of them, including the baby, have had a fascination with their genitals since they have been able to reach them. It is a normal part of them exploring their bodies and we ignore the behaviour as much as possible.
It is important to allow our children to explore their own bodies without us telling them it is wrong or dirty. A child who is prevented from self exploration will more than likely be a sexually inadeqete adult and find it hard to maintain a relationship for long. A child who is raised in an open minded enviornment and taught when it is appropriate, not what, then they are more likely to be well adjusted adults.
These days, we often jump to conclusions about where this behaviour is coming from, and try to stop our kids from doing what is normal, and that is wrong. We need to teach them to be comfortable with their bodies and know their own bodies so that they will be more comfortable with who they are.
Our 5 year old has now pretty much stopped, but that is mostly because she frightened the living daylights out of herself. She was playing in the loungeroom one night after a bath while I was getting night time drinks and all of a sudden, she came running to me crying and saying she had lost a bead. Naturally, it had to be inspected to make sure she hadn't done herself damage, and thankfully, the bead had fallen out itself, but she was still a littel sore for a few days. Seriuosly, you had to be there to see the change from hands in the pants all the time to it being just an absent minded occassional occurance.
Our other girls have all done similar things too, and we actually believe that because we haven't made a big deal about it, that toilet training has been a lot easier as well.
The sweating and going red could be because she still doesn't have the complete arm length to reach properly, which means she as to strain a little more. This would be especially true if she were standing up.
Obviously, if you are concerned about the behaviour or suspect that there is something more going on, then a trip to your gp might be a good idea.