How to add an IP to the DenyHosts whitelist

Create a file 'allowed-hosts' in the 'work_dir' (which can be found in the denyhosts.conf file), located at /var/lib/denyhosts on Ubuntu, containing the IP addresses.
See the example below:

cat <> /var/lib/denyhosts/allowed-hosts 
192.168.1.2 
192.168.1.4 
EOF