Itchiness occurs because some external stimuli has landed on your skin. Your brain reports that and then tells you to remove it through scratching. However, sometimes, scratching actually spreads some of external stimuli, such as poison ivy, and creates even more itchiness. With poison ivy to stop spreading the poison, you need to stop the scratching. To stop the scratching you need to stop the itching. To stop the itching you need to find a salve of some sort.
Spiritually speaking, itchiness can be compared to a temptation. However, scratching a temptation often spreads the poison. The more you scratch, the greater the temptation grows and controls you. The more you do it, the more it covers your spirit and controls you. But how do you stop the itching which stops the scratching? The salve. Allowing God's salve of prayer and God's Word to fill your mind helps battle the itchiness which causes the scratching which spreads the poison of the external stimuli. Yes, just as you have to keep applying the salve until the poison ivy is gone; so you have to keep applying prayer and God's Word until the temptation is calmed. Isn't it amazing what spiritual truths you can learn from life's little irritations?