Itching penis after masturbation

There may be many reasons for this. This is not a major problem but in a few cases, it may be big trouble. So you have to consult a qualified doctor and get his opinion. He will confirm the reasons for this and he may decide whether any antibiotics are to be used.
The following are some of the home remedies.
1. Salt bath: Mix a little salt in just lukewarm water and wash the affected area with that water. It may reduce the problem.
2. There are some specially designed creams for itching on the private parts. They may be available in medical shops. Those can be applied.
3. Take some ice from your refrigerator and wrap it in a cloth and place this on the private part where you have the itching problem. Keep for a minute and repeat. You can do it for 5 minutes at one time and can be repeated 3 or 4 times daily.
It is better if you stop participating in sex till this problem has come down.
But consulting a doctor is a must as sometimes this itching may be due to allergy, urinary track infection and STDs also.

In your case, it would be absolutely necessary to get your blood tested to ascertain the nature of fungus, virus or bacteria and the same can be taken up with the consultation of your family physician. The doctor would prescribe medications depending upon your case. Till you are fully cured, it would be better on your part not to indulge sexual activities with your partner otherwise, she, too, would be affected with your skin disease.
The following points will be helpful in your case-
1) If your doctor is prescribing you some antibiotics after confirming your skin - disorder, the same has to be taken without fail maintaining the scheduled time either eight hours or otherwise as suggested by your doctor. You need to maintain the exact duration of taking such medications so that there is no recurrence of the disease because of under dose.
2) If ointment has been prescribed, ensure its proper application consistently as suggested by the doctor. There should not be any irregularity from your side in course of treatment.
3) Don't be negligent in changing your undergarments regularly and keep your private clean prior to application of ointment as suggested by the doctor.
4) Skin disease originates from the impurity of blood and its purification is necessary to get rid of this disease. In Ayurveda, there is an excellent medicine to eliminate the purity by taking Panch Tikt Ghrit Gugglu to be taken twice daily after your principal meal for at least one and half month to notice desirable results. You may consult an Ayurvedic Doctor to know its benefits. This medication contains Neem, Gugglu, Ghrit, Giloy and many more antioxidants to improve your immune system.
5) Take care of your diet and avoid excess spices and oils till you are recovered.
6) Giloy would help you to enhance your immune system and for that you may consult the Ayurvedic Doctor. He would suggest you dose and duration of taking this Rasayan.

There could be many reasons for such a problem and it would be advisable to consult a doctor so that if it is due to some bacterial or other microbe infection then some specific antibiotics would be needed to cure it.
In most of the cases the reason could be the sensitivity of the soft penis skin to external force creating friction on it and if that is the case then indulging in forceful sexual or masturbating activities will further deteriorate the situation. In this type of situation generally special creams and lubricants are suggested by the doctor or expert sexology specialist but that is of limited use as the effect of friction on breaking of soft surface skin membrane would still be there albeit to a lesser degree.
Keeping good hygiene and regular cleaning of the undergarments using very hot water are some of the ways to avoid the infections which are sometimes responsible for this type of problem. Salt baths, cool compression, abstaining from sex etc are also some of the measures that could bring relief in these conditions.
Some of the medical conditions like Genital psoriasis, Eczema, Allergic reaction, Sexual transmitted infections, genital herpes, syphilis, gonorrhoea, Balanitis, foul-smelling discharge, Yeast infection, Lichen sclerosus, Peyronie's disease, Urinary tract infection etc are the indicative possibilities in such a situation and that is why an experienced doctor would be required to exclude all those things before reaching to a correct diagnosis.