Slane had denied the charge and told the court he had only wanted to frighten his former partner and not harm her.
Colin Slane, 28, was found guilty following a trial at Dundee Sheriff Court last month.
The court had previously heard that 33-year-old Heather Brown suffered massive allergic reactions to a range of products and could die if she did not receive immediate medical treatment.
Slane had denied the charge and told the court he had only wanted to frighten his former partner and not harm her.
Sheriff Richard Davidson sentenced the former Scots Guard to 12 months for the assault, which took place at Ms Brown's Dundee home on 21 January last year.
He was given a further two months for spitting in his ex-wife's face and stamping on the roof of her car. Slane, of Clepington Road, Dundee, had also denied these charges.
Sheriff Davidson said he had no option but to impose a custodial sentence and told Slane: "You were lying to this court when you said you didn't know the extreme nature of the consequences of your actions.
'Particularly wicked act'
"As a consequence of what you did Heather Brown felt dizzy, developed breathing difficulties and a rash that was still there when she saw the doctor some time later.
"She was made to suffer from the symptoms I have described which was a particularly wicked act on your part."
Slane's fiance, Dawn Adamson, wept as she left court and refused to comment on the sentence.
In a brief statement, Ms Brown said: "All I wish to say is that I'm glad it's all over and me and Alan (her son) can get on with our life."
During the trial, anyone entering the court room while Ms Brown was giving evidence had to give a pledge that they were not wearing substances such as deodorant, perfume or after shave.
They also faced being refused admission to the court if they had eaten foods such as peanuts and mints in case it aggravated her condition.
Ms Brown suffers from a rare condition which means that coming into contact with certain products or foodstuffs can cause a severe rash or even anaphylactic shock.
Anaphylactic shock, which is potentially fatal, results in the body producing compounds known as histamines which give rise to symptoms including a swollen throat and face, puffy eyes and drops in blood pressure followed by dizziness and loss of consciousness.