Sometimes there is foam in the urine and sometimes there is not, usually due to urinary tract infection, prostatitis, urinary urgency and urine concentration and other factors. 1. Urinary tract infection: it may be due to urinary tract infection, irritation of the urinary tract mucosa, which in turn causes the phenomenon of sometimes foamy and sometimes not in the urine, and urinary tract infection usually occurs in frequent urination, urinary urgency and other symptoms. 2. Prostatitis: usually due to prostate inflammatory mediators, stimulation of the urine, which in turn causes the phenomenon of sometimes foamy and sometimes not in the urine, prostatitis may also appear pain, urinary abnormalities and other symptoms. 3. Urinary urgency: generally due to urinary urgency, resulting in urine impact on the liquid surface, so that the urine and gas impact each other mixed, which in turn caused the phenomenon of urine sometimes foam sometimes not. 4. Concentration of urine: consider with the concentration of urine, resulting in an increase in the concentration of protein in the urine, which in turn causes the phenomenon of urine sometimes foam sometimes no, urine concentration may also appear cloudy urine color and other symptoms. Foam in the urine may also be caused by other factors, it is recommended that patients go to the regular hospital in time for treatment. In daily life, you should drink more water, pay attention to rest, avoid overwork.