An otherwise dull Mid-Ulster Cup tie exploded to life near the end with three players given their marching orders.
First to go was Dungannon’s Matt Hazley after his rash tackle brought down Caolan Campbell.
Then Campbell got up and pushed Hazley away and that resulted in a second yellow for the Celtic player.
To make matters worse Caolan’s father John raced up the pitch to get involved and was red carded for dissent.
All the drama condensed into the latter stages of what was nothing special on a dismal night.
Apart from the defeat Celtic suffered an injury blow with Declan McVeigh taken off with a painful ankle injury.
“It was a pity the game had to end with three sent off, it really never was a physical game,” said Celtic manager Colin Malone.
“I felt the ref was too hasty in giving Caolan a yellow for pushing because when the incident happened a melee developed and a number of players were pushing each other.
“Then John ran up the pitch to get involved and also ended up with a red.
“That was perhaps the excitement of the entire match. Overall I have no complaints about the result, Dungannon deserved the win over the 90 minutes but I was satisfied with the performance from our team.
“We knew we were not at full strength and all you can do is bring players in and ask them to give 100 per cent and they did just that.
“It was a tough night out there with a constant blizzard during the match and as a result there was not much football played and very few chances.
“We had a few half chances but never really looked like scoring and in the first half our keeper was never really troubled by any of the Swifts attacks.”
Dungannon secured their place in the next round with goals from Chris Lavery and Jamie Tomelty.