today I went to the sea while swimming I coughed...

Dear Customer
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how to treat coughing blood :

1. consult an internal medicine doctor to do the needed medical examnation and determine the treatment pathway
2. stop smoking and avoid alcohol and dusty weather
3. drink plenty of water and vitamin C drinks and honey 
4. take antibiotics such as amoxicillin  ( 2 pills /daily ) for one week
5. take medication to relieve cough such as ivy syrup
6. intial chest X-RAY may be enough to see if there is major injury in lungs or bronchies 
7. if coughing blood lasts occered again or new symptoms appeared , doctor may need to do advanced examnation to determine the cause and treatment pathway

possible causes to your condition :

1. injury by coughing force to oral or bronchal area ( heavy coughing )
2. smoking
3. lung infections 
4. lung chornic diseases 

needed medical examnation :

1. physical examnation by doctor 
2. blood and blood chemistry tests
3. chest X-ray
4. blood gases tests 
5. oral cavity and bronchal endoscopy 

our advices :

please follow our advices , and its better to consult doctor especially if the symptoms appears again or new symptoms appeard 
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Kind Regards