My son is currently taking colostrum and sambucus. Colostrum he takes everyday. Sambucus only when he starts to cough and gets phlegmy.
My son used to fall sick very often at infant care until a mummy in the forum introduced me to colostrum and sambucus.
Now he seldom falls ill and even if he does, he recovers quite quickly.
I buy them from the website which that mummy introduced or you can refer to her thread: To answer all the PMs (about STON..supplements, boosting my boy's immune system, etc)