(main reason) BECAUSE it isn't RECIEVING enough water!**
The BEST thing is to always constantly DROWN yourself in water because though water has 0 calories and 0 carbohydrates and 0 proteins, it has MANY vital necessities that the body NEEDS and when your body isn't getting enough, it begins to hold it.
1) Yes, not getting enough water will make your body hold onto water weight because it is a survival mechanism.
2) If you are working out, you will lose water weight. If you weigh yourself after a workout and then weigh yourself first thing in the morning, you might be up a few pounds because of the water lost during the workout was replenished.
3) Also with working out, if you are new to working out, have done a very long work out (like long runs or 3 hour spin class or something), or lifting heavy, your body will retain water for a few days to repair muscle.
4) That typical time of the month for women, when your pants dont fit they way they did 2 weeks ago.
5) Not enough protein, too many carbs. Being a vegetarian i learned this the hard way and my ankles were the first to swell up and then other signs showed the following day. Also carbs hold onto water, this is normal, carbs just doing their job.
6) Too much sodium, just salt being salt and absorbing water like salt does.
The side effects of allergy medications keep some people from using them. Natural remedies can be a great alternative, but some are more effective than others.