We do not abstain from objects themselves, we abstain from specific acts done in connection with these objects. For example, what does "abstain from alcohol" mean? Does it mean to not have anything to do with alcohol? Devoid of any context it is impossible to tell. It could mean not using alcohol in one specific way while allowing other uses of alcohol. For instance, it could mean not drinking alcohol but allowing its use as an antiseptic. Likewise with "abstain from blood." It could mean not eating blood but allow for other uses of blood that don't involve eating it.
The bare statement "abstain from blood" devoid of any context is ambiguous. How does one comply with it? Though short, the statement fails to stipulate what blood must be abstained from, and it fails to stipulate what abstention (or abstentions) is required. Are we to abstain from looking at, thinking about, touching, smelling, or talking about blood? By itself the statement is impossible to follow for it is impossible to universally "abstain from blood." Afterall, our very lives are dependent on the blood flowing through our veins. If the abstention is not universal then we are forced to look elsewhere in applicable scripture to see how Christians should abide by the Apostolic Decree to abstain from blood. If one does that it becomes clear that the blood Christians are required to abstain from is the blood of slaughtered animals and the abstention required is not eating this blood.