Both players featured regularly for Town last season in the disappointing campaign that saw the team relegated from League One.
However, they are both yet to feature this season with 22-year-old Wildig only making the bench a handful of times.
Boss Mellon said: "We believe that Aaron and Dave would benefit from going and finding some first team football.
"We have circulated the lads and spoken to them because we feel we are okay in central midfield and it's a long time since they have played a first team game.
"They are two good guys and two good footballers and they need to go and play. Hopefully we may have one or two options for them."
Former Cardiff midfielder Wildig made 33 appearances last season.
McAllister appeared 29 times but the 25-year-old hasn't featured since picking up an ankle injury in March.
Despite being made available for loan, Mellon insisted it doesn't mean the pair's careers at Shrewsbury are over.
He said: "Football moves so quickly, you would be wrong to write anyone off. Everyone who is here is still in my plans.
Meanwhile, Mellon believes his entire defence must work together to deal with Swiss keeper Jayson Leutwiler's tendency to punch at crosses rather than catch them.
He said: "This is something that we have had to get to used to. Jayson is a continental goalkeeper and chooses to punch more than we'd expect.
"Personally I would prefer it if he caught it but at the end of the day it's what the lad feels is the best way to handle crosses."