Bollinger Bands are volatility curves used to identify extreme highs or lows in price. Bollinger Bands establish "bands" around a currency's moving average, using a set number of standard deviations around the moving average. Creator Jon Bollinger recommends the following:
Touching a high or low band doesn't necessarily mean an immediate trend reversal. Bollinger Bands adjust dynamically as volatility changes, so touching the band just means prices are extremely volatile. Use Bollinger Bands with other indicators to determine the trend's strength.