Hello Rifampicin, isoniazide pyrazinamide, ethambutol are the ingredient in fixcom-4 . The red color allergy may be due to any of these drugs ( but this is uncommon ) . Since you are having PTB ,so the treatment is very important , don t stop this anti tubercular treatment . Since when such case visit I prescribe montelukast= fexofandine when allergy develop . But this is a prescription drug , so consult your doctor . Sometimes I have also noted that usually allergy is associated with PTB ,so treatment is important. Take a full course and remain in contact with your doctor. Good luck.