It is normal for the eyes to get watery after using the mascara which contains a lot of stimulating irritates. The irritates will make your eyes get uncomfortable. Some people's skin is sensitive which will make your eyes get dry and red easily. You should better not do the make up often by using the mascara and other things. You could use the eye drops with anti-inflammation to reduce the watery eyes.
Unfortunately, as far as i am concerned, your eyes are infected by the mascara. Some mascaras are made of chemicals, even the plastic. So by wearing them, they can make your eyes be in the risk of infection. In addition, it's the easy to spread the bacteria to your eyes, which can disorder your tear system and finally make your eyes watery. In some serious cases, it can even give rise to redness, itching, irritation, and a characteristic creamy discharge in your eyes. Accordingly, making them not be with allergies is important. And you'd better not wear mascara all the time to give your eyes a period of time to have a rest. To solve your situation, you can drop some eye drops in your eyes, and it can relieve your symptom. But if the symptom is not disappear or even get worse, maybe you should ask the doctor for help.
May be you use your mascara in a wrong way, or you are allergic to some ingredients of your mascara. You can show your mascara to the doctor to determine if you are allergic to it. If so, you should throw your mascara, and to change a new one that will not cause allergy, or not use mascara any more. If not, you can turn to an oculist to check if there is other medical condition associated with watery eyes. If you have the habit of rubbing your eyelashes with mascara, some mascara will slip into your eyes, leading to irritation that makes your eyes watery. Besides, it is better for you to change your mascara every three months, for mascara accumulates bacteria after long time of use.