Another thing that repels foxes are substances that offend their smell. Foxes hunt basically with the use of their noses and so they do not like sharp smells that throw their sense of smell off balance. Strong smelling substances such as ammonia and citronella can have a burning effect when inhaled. Foxes are territorial and will not go near a place if they sense the presence of a predator. Urine is one of the signs used to mark territories by animals therefore this method could work in ensuring that foxes stay away. Again, the problem with this method is that it needs constant reapplication as the effect wears off quickly. Another downside to this method is the fact that ammonia has a pungent smell which can be offensive to humans and household pets. The chemicals in these substances can also potentially cause serious health issues. Children are also at risk of mistakenly ingesting repellent if they come into contact with it.