After talking to Dr. Abraxas you learn about the potion that will cure cat allergy.
It only has 103 ingredients! Nice to have a little different from those usual three-ingredient puzzles.
Oh, the doctor already has hundred of them... Well, you still should get the three ingredients:
When Justin has all of these, go talk to Dr. Abraxas.
Unlike normal walkthroughs, in Nice Game Hints you can select just the puzzle you want hints for. Here are listed the puzzles for "Allergy potion" in Justin Wack and the Big Time Hack. The guide you choose only contains information about that puzzle, reducing possible spoilers for other puzzles.