My brother and I just started playing Elder sign and a quesiton came up reguarding Ithaqua and when exactly this penalty for using unique items and spells comes into play.

For example, with a card that heals.. if you were to use an ability that heals while you were at 1 stamina. Would Ithaqua's ability kill you before you recieved the healing.

When is the stamina pentaly resolved?

To be specific, I have 1 stamina, I use health stone. Do I die from Ithaqua's ability before I am actually healed by the card? Or does the card heal me to full and then I suffer that stamina penalty?

You lose 1 Stamina each time you spend a unique item or spell, so the mere use of the item is what triggers the -1 Stamina. Therefore, I would have to say the Stamina loss occurs before any effects gained from the item. In your case, I would have to say you die when you use your item.

In my opinion, the effect of using a card to heal yourself occurs immediately after discarding the card. With that said, Ithaqua's effect also occurs immediately after discarding the appropriate card. To me the logic would follow that both of those immediate effects would occur simultaneously. I think of it like cutting a small hole in the bottom of a water filled bucket at the exact same time you began to add additional water to it. If you are filling the bucket at the same rate it is losing water, the water level would not drop and would therefore never be technically empty (or in this case the investigator would not technically run out of life, as it is being drained at the exact same rate as it is being filled). Just my two cents.

I don't think there's any specific timeline for this. I'd apply them both at once, and treat it it as a net gain. player health = ( healing gain - Ithaqua's deduction ).